Methods and apparatus for making optical devices including microlens arrays

Abstract

Microlens arrays, especially useful for optical coupling in optical switches of fiber optic telecommunications systems are produced with optical quality requisite for such applications with a replicating tool. This tool is made using a form tool set up in a rotating spindle of a precision air bearing milling machine at an angle of inclination such that the point of zero surface velocity is maintained outside of the surface of substrate machined to make the tool for replicating the arrays. The tip of the form tool has a profile corresponding to the profile of the lenses of the array, such as a generally circular profile having a radius centered at the axis of rotation of the form tool. The form tool is reciprocated with respect to the surface so as to form cavities of the desired profile, radius and depth which corresponds each identical lens of the array. To provide arrays the form tool is raised and the substrate is translated to preprogrammed positions. When these positions are reached the reciprocation and cutting action of the tool is repeated. The replicating tool containing cavities defining the lenses of the array which provides a master. The master may be used to replicate identical arrays. Lenses so formed may be positive with convex surfaces. Arrays of lenses, which are negative and have concave surfaces, may be made using an intermediate master replicated from first master. The profile of the lenses may be altered by changing the shape of the form tool cutting surface or by translating the substrate during reciprocation of the formed tool as the profile of each cavity is being machined. In addition to lenses having optical power, reflectors with desired power may also be made with the machined master or intermediate master.