The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Mar. 21, 1989
Filed:
Feb. 11, 1988
James R Leger, Groton, MA (US);
Wilfrid B Veldkamp, Lexington, MA (US);
Miles L Scott, Bedford, MA (US);
Massachusetts Institute of Technology, Cambridge, MA (US);
Abstract
A diffractive lenslet array receives light from multiple lasers. The lenslet array is spaced apart from a partially reflecting mirror by a distance Z=nd.sup.2 /.lambda. where n is an integer or half integer, .lambda. is the laser wavelength and d is the spacing of the lenslets in the array. In a preferred embodiment the apparatus is a unitary design in which the lenslets are etched into one surface of a substrate and a parallel surface is coated to form the partially reflecting mirror. The lenslets abut one another to produce a fill factor (percentage of array containing light) close to one and each of the lenslets is a multistep diffractive lens. Diffractive speading over a round trip distance from lasers to mirror and back again causes feedback light from a single lenslet to couple into adjacent lenslets. The light from all the lenslets is coupled back into the laser waveguides efficiently only when the wavefront at each of the lenslets is flat, that is, when the phase of the feedback is uniform across a lenslet. Uniformity is achieved when the separation between lenslet array and mirror is the Talbot self-imaging condition set forth above.