Abstract: Aspects of the present disclosure describe systems, methods, and structures for aberration correction of optical phased arrays that employ a corrective optical path difference (OPD) in the near-field of an OPA to correct or cancel out aberrations in emitted beams of the OPA including those reaching far-field distances by generating a spatially-varying OPD across the aperture of the OPA that is substantially equal and opposite to an equivalent OPD of the aberration(s).

Abstract: A mechanical face seal includes a seal face member which is secured in fixed rotational relationship and sealed with respect to one component by means of a resilient bellows unit, said bellows unit being attached at one end to the associated component and at the other end to the seal face member, the seal face member being biased into sealing engagement with a second seal face member by compression of the bellows unit, the bellows unit defining a plurality of convolutions, a convolution in a portion of the bellows unit subject to higher stressing having a pitch which is greater than and/or a depth which is less than that of a convolution in a portion of the bellows unit subject to lower stressing, thereby evening out the stress distribution in the bellows unit when in operation.