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Browse Prior Art Database

ALIGNMENT TECHNIQUE FOR SEALED OPTICAL SYSTEMS

IP.com Disclosure Number: IPCOM000006460D
Original Publication Date: 1992-May-01
Included in the Prior Art Database: 2002-Jan-04
Document File: 2 page(s) / 132K

Publishing Venue

Motorola

Related People

John S. Scavarda: AUTHOR

Abstract

This publication describes a technique for active align- ment of hermetically sealed optical systems. Typical sys- tems containing optical components which must be isolated from their external environment include evacu- ated chambers such as dewars and target detectors, mon- itors of harsh manufacturing processes involving caustic chemicals or extreme environmental conditions, and underwater photographic or video cameras. The need for the periodic purging of impurities, replacement of resilient seals, or for precise pre-seal alignment is elimi- nated. Three techniques which are currently applied in lieu of this invention, and the disadvantages of such sys- tems, are described in the following paragraphs.

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MOTOROLA INC. Technical Developments Volume 15 May 1992

ALIGNMENT TECHNIQUE FOR SEALED OPTICAL SYSTEMS

by John S. Scavarda

  This publication describes a technique for active align- ment of hermetically sealed optical systems. Typical sys- tems containing optical components which must be isolated from their external environment include evacu- ated chambers such as dewars and target detectors, mon- itors of harsh manufacturing processes involving caustic chemicals or extreme environmental conditions, and underwater photographic or video cameras. The need for the periodic purging of impurities, replacement of resilient seals, or for precise pre-seal alignment is elimi- nated. Three techniques which are currently applied in lieu of this invention, and the disadvantages of such sys- tems, are described in the following paragraphs.

  The most common technique is to seal the entire conventional optical system in an airtight bag, case, or housing. Active alignment of the system is often cum- bersome due to the bulk or contiguration of the external enclosure. Since this method does not provide a her- metic seal, periodic removal of the optical system from the enclosure is necessary to purge water or other chem- ical impurities. Any condensation of impurities prior to purging can cause permanent damage to optical com- ponents or alignment mechanisms. A desiccant is often placed in the enclosure to control the relative humidity over the useable lie of the desiccant.

  A less common technique is to fabricate a custom optical housing in place of the conventional housing. Its exterior surfaces, including an environmental window, are treated to prevent corrosion or physical damage. The moveable portions of the alignment mechanism are sealed with resilient O-rings. This configuration provides for simpler alignment than does the first method. However, it does not provide a hermetic seal and requires periodic servicing to purge impurities and replace worn seals.

  The final technique requires that the optimum align- ment be determined and accomplished prior to scaling of the optical system. A true hermetic seal may be employed using glass, ceramic, or metal. The housing has exterior surfaces, including an environmental win- dow, treated to prevent corrosion or physical damage.

This approach is applicable only to situations where a single alignment/focusing process is su@ient. Such sys- tems typically cannot be activated until after they are sealed thus preventing the active alignment process.

  Utilization of the invention described in this publi- cation requires that the existing or new optical system be contigured to provide the needed alignment via rota- tion of the focusing component. This adjustment method is used commonly in optical desig...