Diffractive beam steering system with high efficiency
AssigneesBeam Engineering for Advanced Measurements Co., Defense Advanced Research Projects Agency (DARPA)
InventorsRobert Winsor, Paul Calhoun, David Roberts, Nelson Tabirian
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Abstract
Opto-mechanical assemblies, systems, devices and methods for pointing laser and other optical beams, and for directing the field of view of sensors are disclosed. The assemblies consist of thin rotating optical elements of a type that diffracts the optical beam over a wide field of regard in two dimensions, and the angle of incidence of the optical beam or line of sight impinging on the optical elements are dynamically controlled maximizing the diffraction efficiency of the optical elements.
Claims5
A diffractive beam steering system that is independent of polarization state and preserves a cross-section of a deflected optical beam and maintains high efficiency for all deflection angles, comprising:
- an optical beam;
- a system of at least two diffractive beam deflectors, said diffractive beam deflectors each comprising at least two cycloidal diffractive waveplates, one of which diffracting light of one handedness of circular polarization, and another one diffracting light of the opposite handedness of circular polarization;
- said at least two diffractive beam deflectors arranged at predetermined angles with respect to each other such that an angle of incidence of the optical beam onto a first diffractive beam deflector is at a Bragg angle for both cycloidal diffractive waveplates constituting the first diffractive beam deflector to maximize efficiency for the propagation direction of an incident beam, and a second diffractive beam deflector is at a Bragg angle for both cycloidal diffractive waveplates constituting the second diffractive beam deflector to have maximum efficiency for the propagation direction of the beam diffracted by the first diffractive beam deflector, and each subsequent beam deflector is optimized to have maximum diffraction efficiency for the beam optical diffracted by each preceding diffractive beam deflector;
- and
- means for rotating the at least two diffractive beam deflectors, such that rotation axis of each diffractive beam deflector after the first diffractive beam deflector is parallel to the direction of propagation of the optical beam after each diffractive beam deflector has been diffracted by a previous diffractive beam deflector, for all rotational positions of the previous diffractive beam deflector.
Dependencies are inferred from the claim text.