Optical filter assembly and the method of stabilizing the filtering characteristics of the interference filter

• Main Authors: ORTIZ, MARCOS GERMAN, MOSKOVICH, JACOB, CHU, POLLY W, RANALLIN, ELISEO ROMOLO, FABER, MARGARET KATHLEEN
• Format: Patent
• Language: English
• Published: 21.03.2003
• Edition: 7
• Subjects: DEVICES OR ARRANGEMENTS, THE OPTICAL OPERATION OF WHICH ISMODIFIED BY CHANGING THE OPTICAL PROPERTIES OF THE MEDIUM OF THEDEVICES OR ARRANGEMENTS FOR THE CONTROL OF THE INTENSITY,COLOUR, PHASE, POLARISATION OR DIRECTION OF LIGHT, e.g.SWITCHING, GATING, MODULATING OR DEMODULATING; FREQUENCY-CHANGING; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; NON-LINEAR OPTICS; OPTICAL ANALOGUE/DIGITAL CONVERTERS; OPTICAL ELEMENTS, SYSTEMS, OR APPARATUS; OPTICAL LOGIC ELEMENTS; OPTICS; PHYSICS; TECHNICAL SUBJECTS COVERED BY FORMER USPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ARTCOLLECTIONS [XRACs] AND DIGESTS; TECHNIQUES OR PROCEDURES FOR THE OPERATION THEREOF

A temperature compensated optical filter assembly comprising a plurality of thin films having temperature dependent indices of refraction which are deposited on a glass substrate so as to form a conventional interference filter thereon. The glass substrate is adhesively coupled to a metal holder such that the deposited thin film interference filter is interposed between the glass substrate and an adhesive layer distributed along a mounting surface of the holder. Thus, a first thermal mismatch stress is applied by the glass substrate onto an inner layer of the interference filter and a second mismatch stress is applied by the holder onto an outer layer of the interference filter, wherein the first and second mismatch stresses depend on the temperature of the filter assembly. The glass substrate, the adhesive, and the holder are preferably formed of materials having mechanical properties such that the first and second mismatch stresses compensate for the effects of the temperature dependent indices of refraction of the thin films so as to uniformly maintain the spectral performance of the filter assembly in response to a change in temperature. In one embodiment, an additional degree of freedom is obtained by electro/magneto-strictively pre-stressing the thin film stack during the formation thereof. In another embodiment, an active stress management system is utilized.