Patent ID: 8116001
Filing Date: 2012-02-14
Classification: G02B

Abstract:
1. A light pipe for transmitting light signals from one of its ends, referred to as its inlet surface, to its other end, referred to as its outlet surface, facing towards the eye of a user for viewing a virtual image, the light pipe comprising: a diffractive component formed directly in the inlet surface, the diffractive component being an element satisfying the equation of an aspherical component of revolution of the “kinoform” type, wherein the diffractive component of the pipe has power situated in a range D(Thresh,X) defined by: where the range D TXT (X) corresponds to the range (ΔP) of diffractive power values of said component for which the value of the overall transverse chromatic aberration is below an acceptable transverse chromatic aberration threshold X equal to or less than 6 arcmin, transverse chromatic aberration being expressed in the form of an angle; and where D OPTDIF (Thresh) is a power range determined as a function of a diffraction efficiency, written “Thresh”, that corresponds to an acceptable value for 1/R k , for given fabrication tooling, R k being the ratio between the peak value of the intensity of the point image of the diffraction order k under consideration, and the peak value of the intensity of the point image of the design diffraction order.