------------------------------------------------ INSTRUMENT / OPTOMECHANICAL INFORMATION EXCHANGE ------------------------------------------------ March 2000; Volume 2, Number 3 Edited by Roger S. Reiss [EMAIL PROTECTED] IN THIS ISSUE: Instrumentation at Photonics East Space Communication Receiver Metal / Glass Bonding Thin Wall Brazing Micro Beam Deflector To subscribe or unsubscribe ----- Instrumentation at Photonics East At Photonics East, 5-8 November 2000, there will be numerous sessions of interest to the instrumentation and optomechanical community. Please take a look at the call for papers at http://spie.org/info/pe/ for more information. Within the "Intelligent Systems for Advanced Manufacturing" symposium you'll find the following conference. This is a great opportunity for anyone involved in the field in the Northeast to participate in and support our community in the region. If you live within a couple hours' drive of Boston, please plan to attend. A good turnout (both in papers submitted and people showing up) will help to establish this conference for years to come. Abstract due date is 10 April 2000. Optomechanical Engineering Northeast (RB14) Conference Chair: Mark A. Kahan, Optical Research Associates Cochairs: Roger S. Reiss, R.S. Reiss Associates; Daniel Vukobratovich, Raytheon Systems Co.; Paul R. Yoder, Jr., Consultant in Optical Engineering This will be a two-day engineering conference on new models/methods, enabling technology, and emerging hardware. Paper contributions are solicited on, but not limited to, the following topics: - modeling - thermo-optical modeling - structural modeling - integrated optical and AO modeling - contamination, radiation and spacecraft charging hardware - optomechanics of photonic devices - optomechanics of MEMS, problems and hardware - OM of telecommunication systems - aerospace updates ----- Title: Space Communication Receiver (Part Two; Part One appeared in last issue.) Key words : receiver space communication Source: "Receiver Front End (RFE) for Optical Free Space Communications" by Ulrich Hildebrand, ANT Nachrichtenhnik GmbH, D 71522 Backnang, Germany; SPIE Proceedings, Vol. 2210, page 96. The RFE consists of a housing, an optical system, lens and the detector circuit (and detector circuit mounting provisions). The reference article discusses the mechanical and thermal aspects of the design, necessary to obtain and maintain the required angular stability. The lens mounting (a must see illustration in the reference article) consists of lens (Fused Silica) and the lens barrel (Titanium). Consideration was given to a bonding but was abandoned because of out gassing and qualifications problems (Editors note: I have been working with JPL / NASA and have a recommended material, 'RTV 566 A / B'. Any questions on application of this material or any RTV or epoxy, please email <[EMAIL PROTECTED]>). The lens is held in the lens mount by two sets of springs; axial and radial. The radial springs keep the lens centered using a concentric pre loading. The axial springs keeps the lens against the mounting shoulder using an axial pre load. The spring pre loads forces are determined by the acceleration of vibration testing and or lift of acceleration. The RFE has an operational temperature range of 20 + / - 8 * C. There is good thermal conductive coupling to the optical bench of 1 W / K with an RFE power dissipation of 1.3 W. The thermal design is a compromise between mechanical integrity (stiffness) with good thermal conductivity and a lightweight design that relies on radiant space cooling. The housing is coated with a black oxide ceramic layer with a low out gassing property and an emmisivity of 0.8 The conductive thermal interface is concentrated at the rear mounting foot. A thermal path is required between the detector circuit and the rear foot because the detector circuit dissipates the largest part of the dissipated power (the conductivity of the Titanium housing is not adequate). This path consists of a thermal conductor plate made of MoCu with a copper foil beneath this plate and the detector circuit. MoCu has a CTE close to Titanium with conductivity of Aluminum. The rotary mounting joints used during alignment are clamped after alignment procedure is complete in order to minimize temperature differences at these locations. ----- Title: Metal / Glass Bonding Key words: glass metal bonding Source: Jet Propulsion Laboratory (NASA), Pasadena, CA Jet Propulsion Laboratory (NASA), Pasadena , CA has designed and developed a metal-organic film which can be thermally bonded to glass pieces and then soldered or welded to form a hermetic seal. The film is applied as an ink which consists of silver neodecanoate in xylene. The relative amounts of ingredients are selected to control the desired viscosity (application is by a simple scribing pen). The ink like mixture is deposited in matching pattern on two pieces of flat glass. The pattern on the lower glass peice is a slightly wider line than the line on the lower glass. The glass pieces are heated in air to 260 * C to evaporate the xylene and decompose the silver neodecanoate, leaving adherent patterns on the glass pieces. Solder paste is deposited on the wider line and air dried. The upper glass is placed over the lower glass with its silver metal pattern resting on the solder paste. The glass pieces are clamped together and soldered, using the standard thermal cycle, specified for the solder. If the seal location requires minimum heating, the heat for decomposition and the soldering can be supplied by a well controlled laser beam which will confine the high temperatures to the sealing region. ----- Title : Thin Wall Brazing Key words : brazing thin wall Source: "Brazing Book" by Handy & Harman, http://www.brazingbook.com For fabrication using 'thin wall brazing' consideration is given to: - metals being joined - design of the joint configuration - ambient operating environment - economics of the fiiler material If the parts being brazed are dissimilar metals, a filler material should be used that will 'wet' both metals. The filler material chosen should flow readily over both metal surfaces and securely bond to each metal. Molten filler material has the capability to alloy with a base metal. Consideration should be given to the difference in thermal expansion of the two dissimilar metals. This difference will effect the initial clearance chosen for assembly heating during brazing. To compensate of this mismatch, start with a loose fit, so that when the heated assembly reaches brazing temperature, the the gap separation is close to what was desired. Ideal joint clearance for brazing ranges from .001" to .002". For wider clearances, a filler material can be formulated to specifically fill a loose fit. A filler material with a narrow melting range is extremely hard to find. A filler material with a broad melting range is slow and sluggish, enabling the filler material to fill the wider gap. For thin wall brazed assemblies consideration should be given to any vibration environment since vibration will fracture a brazed joint and cause elongation of a fracture. For economic reasons (usually not a factor in precision instruments and devices), selection of the filler material should be with the lowest silver content that will achieve the requirements of the 'thin wall brazing' joint. ----- Title : Micro Beam Deflector Key words : micro light deflector Source : "Micro-opto-mechanical beam deflectors" by Steffen Glocker, Rolf Goring, and Torsten Possner, Fraunhofer Institute for Applied Optics and Precision Engineering Jena, Jena, Germany, gloeckne@iof,fhg.de, Opt. Eng. 36(5) 1339-1345 (May 1997). Abstract: "...(Since) the required displacement of the micro-optical components for efficient beam manipulation is quite small, high-speed actuators with small electrical power consumption can be used (for light beam deflection and light beam modulation)...The combination of micro-optical components already available and (the use of) semi classical piezoelectric actuators (allows for) new types of switching and modulation systems for a very broad spectrum of applications." In the reference paper, a number of micro-optical systems concepts are presented; - steering of coherent and incoherent beams - general aspects of micro-optical beam steering - beam scanning systems (especially with Gaussian distribution) - deflecting incoherent beams (emitted by multimode fibers) - systems integration and applications - conclusions and proposed future work - system requirements light losses resolution (number of resolvable beams, behind the scanner) cross talk (between different steering positions) steered beam quality switching time modulation rate The actuation system is a critical area for the micro-optical scanners. Scanning is achieved by the mechanical movement of the optical elements. The switching times are restricted by the mass of the optical elements and the amount of the movement required. The micro-optical components used are from several tens of milligrams up to several grams in mass and many actuators are too weak for load (electrostatic, thermal. or magnetic (others) actuators). Some applications require switching times of a few milliseconds, which can utilize piezoelectric actuators (these are actually stronger than required). Bimorph piezoelectric layers can achieve movements of 100 um and even more. The actuator consist of two connected piezoelectric layers acting like a bimetalic strip operating in a bending mode. Translation can be achieved, instead of bending, in one direction, if two of the bimorph layers are combined to form a parallelogram. This suppresses movement in the unwanted direction. A planar and cylinder arrangement of the parallelogram has the capability of two-dimensional translation. Linear sensors can be used for position detection and direction. Displacement can be adjusted using various lengths and material stiffness.. Maximum displacements of 20 to 200 um with resonant frequencies of 0.1 to 0.6 kHz and switching times of a few milliseconds is achievable. ----- TO SUBSCRIBE: If you received this from a friend, and you're not subscribed to SPIE's INFO-OPTOMECH list, you can receive it for free each month. Just send e-mail to [EMAIL PROTECTED] with the following in the body of the message: subscribe info-optomech TO UNSUBSCRIBE: Send e-mail to [EMAIL PROTECTED] with the following in the body of the message: unsubscribe info-optomech
