Monolithic linear variable filter and method of manufacture

Abstract

A process suitable for forming multi-layer (up to at least several hundred layers) monotonic/linear variable/wedge filter coatings on a single substrate surface and for forming monolithic filter assemblies which incorporate such filters, is disclosed along with the designs for such filters. The monolithic process uses radially variable filter fabrication techniques in combination with ion-assisted deposition to form stress controlled, radially variable filter coatings of the desired varied optical profile, preferably using high and low index materials stich as tantala and silica. Stress is minimized by balancing the amount of ion assist and the coating rate. Slices are cut radially from the substrate to form quasi-linear variable filters. Other coatings such as, but not limited to, a wide band hot mirror can be formed on the opposite surface of the substrate from the radially variable LVF method. The method forms complex multi-layer thick filters with high yields on a single substrate surface such that the filter is free of precession or sideways leakage of light between the parallel surfaces. Also disclosed is an optical filter having stacks arranged so that the magnitude of the characteristic center wavelength of each stack increases from stack to stack along the desired direction of traversal of incident light through the filter. As a result of this sequential construction, diffuse leaks are blocked from transmission through the filter. The diffuse leak-suppressed filter can be formed by various processes, including the monolithic process.