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SPIE Optifab 2015 news and photos

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SPIE Optifab 2015 exhibition
Booths at Optifab 2015 saw a more than 20% increase in traffic over the 2013 event.
Read exhibitor comments and see more Exhibition photos below.

 


Off to a great start!

SPIE Optifab, the largest optical fabrication event in North America, was off to a great start on Monday, with strong registration numbers going in to the event. Conference chairs this year are Julie Bentley, University of Rochester, and Sebastian Stoebenau, OptoTech Optikmaschinen GmbH.

First-day presentations met with enthusiasm and many questions from engaged audiences. Talks demonstrated the wide range of materials and processes used in optical manufacturing and their applicability beyond this field, setting the stage for an interesting week of information exchange. Among topics at Monday's sessions:

 

Grinding and polishing: processes

Laser Megajoule at SPIE Optifab
Speakers reported on new processes that
advance capabilities across multiple fields.
Laser Megajoule at SPIE Optifab

Among several sessions on grinding and polishing processes, the use of additive manufacturing processes to fabricate lapping tools was discussed by Wesley Williams of the University of North Carolina at Charlotte (9633-1). He demonstrated that high tool wear resulted in this approach being best used for short feasibility studies and not long production runs.

Sivan Salzman of the University of Rochester demonstrated that a magnetorheological fluid approach using acidic fluids can offer a significant reduction in surface artifacts and roughness for near IR materials (9633-4).

Speakers from the CEA and the Laser Megajoule also presented. Cedric Maunier discussed a study of colloidal silica slurries for fused silica optics finishing and determined that slurry concentration drives surface quality (9633-5). Phillippe Cormont shared results from a CO2 laser post-inspection process used to remove scratches on fused silica optics (9633-7). Scratch removal was possible although the presence of a heat-affected zone did result in surface anomalies.

In two presentations, Abagail Hooper of Nanophase Technologies described the impact of particle size and the use of accelerants in alumina slurry polishing of thermoset and thermoplastic resins (9633-2), and illustrated that a stabilized slurry could allow for a deterministic fused silica polishing process over the course of several days (9633-13).

Sapphire continues to draw interest particularly as a cover glass in consumer electronics applications. Mark Walters of Optimax Systems described a polishing process which achieved 3Å root-mean-square (RMS) roughness and a 50% cycle time reduction for 12" sapphire windows (9633-14).

Among presentations by equipment manufacturers, Paul Murphy of QED Technologies described a method to correct for mid-spatial frequency surface effects (9633-9) while Chris Maloney, also of QED Technologies, demonstrated a fine figure correction process suitable for a final finishing step for soft materials (9633-10). Other topics in the session included asphere manufacturing, stem polishing, and the importance and recent developments in centering technology.

 

Grinding and processes: metrology

Coffee break at SPIE Optifab
Opening day coffee breaks offered the
opportunity to see who is here this year.
Coffee break at SPIE Optifab

Among presentations on metrology, in an attempt to address tool wear concerns, Michael Cahill of OptiPro Systems described the design of an ultrasonic diamond grinding tool and shared data illustrating the resulting improved tool lifetime (9633-19).

The use of femtosecond lasers in polishing optical materials and the resulting oxidation effects was the subject of the presentation from Lauren Taylor of the Rochester Institute of Technology (9633-20), and Hideo Takino discussed the development of a polishing spring plate process for polishing cube mirrors for use in lunar distance studies (9633-21).

Christina Canavesi of LighTopTech Corporation described the development and initial testing of a Gabor-domain optical coherence microscope (GBOCM) incorporating a dual-axis MEMS scanner (9633-21). GBOCM offers an attractive compromise between ultrasound technology which provides good depth scanning capability and confocal microscopy which provides superior resolution at the cost of scanning depth. The development of customized driving signals for the scanner resulted in avoiding the resonance frequency and the subsequent ringing effects meaning that post-processing of the data was no longer necessary. Data obtained from samples including human skin, a human cornea, and a retroreflective film showed the promise of the technique.

On the topic of scanners, Virgil-Florin Duma of the Aurel Vlaicu University of Arad described the development of lightweight hand-held, single-axis galvo scanner probe systems for biomedical and industrial imaging applications (9633-24). Diverse examples cited included imaging teeth for dentistry applications and the detection of metal fracture for industrial manufacturing processes.

Coffee break at SPIE Optifab
Coffee break at SPIE Optifab

 

Plenary talk: 3D printing of optics

Joris Biskop and Julie Bennett
Conference chair Julie Bentley introduces the first plenary speaker, Joris Biskop.

The use of additive manufacturing to print optical elements provides opportunities and presents a number of challenges. In his plenary talk, Joris Biskop of LUXeXcel Group BV discussed this new approach to optics fabrication, detailing his group's efforts to bring inkjet printing of optics to the market.

This method provides the ability to produce smooth, transparent structures at production speeds, coupled with the flexibility to quickly incorporate changes to test design variations. The inkjet printing nature of the approach currently limits output to optics with at least one planar surface, and print height is limited to 25mm. The process has the added advantage of no post-polishing process being needed.

Next steps include development of a double-sided printing scheme to circumvent the planar geometry limitation, expanding the physical footprint of the optics, and investigating new materials and coatings.

Although this approach is in its early stages, Biskop's presentation demonstrated that it has potential for production-level use in specialty optics.

 

Plenary talk: laser polishing of glass

Christian Weingarten
Christian Weingarten

Laser processing of glass continues to garner much industry interest given the prevalence of glass in such areas as consumer electronics, medical devices, and the automotive industry. In his plenary talk, Christian Weingarten of the Fraunhofer-Institut für Lasertechnik noted that laser polishing of glass offers a contactless method whose processing time is independent of the surface geometry of the work piece.

The technique uses a continuous wave CO2 laser with a 7mm-10mm beam size to heat glass to a temperature near but below its vaporization temperature thereby allowing surface tension effects to smooth out surfaces. A pyrometric thermal measurement arrangement monitors glass temperature during the process. Material feed rates vary from 1-5mm/sec depending upon the material being processed. To date, work has been done with fused silica, BK7, and flint glass (Ohara S-TIH6).

The process has been shown to work on flat and curved surfaces and has been extended for use in edge polishing where it has the added benefit of healing micro-cracks.

Whereas a continuous laser output is required for polishing, a pulsed CO2 laser source was used to develop a precision laser ablation process. Weingarten demonstrated controlled ablation depths of 4nm-20nm on glass with no increase in surface roughness over the pre-processing values.

Future work on these two processes will revolve around developing a process chain for use with conventional processing methods to enable integration onto the factory floor. The work demonstrates that laser processing does provide a path forward in processing of this particularly difficult-to-machine material.

 

Kudos! Kidger Scholarship awarded

Julie Bennett, Tina Kidger, Eric Schiesser, Jannick Rolland
Eric Schiesser was awarded this year's Kidger Scholarship. From left,
conference chair Julie Bentley, Tina Kidger, Schiesser, and Jannick Rolland.

At the close of the plenary session, Tina Kidger of Kidger Optics Associates presented the 2015 Michael Kidger Memorial Scholarship to Eric Schiesser of the University of Rochester, a third-year PhD student working in the lab of SPIE Fellow Jannick Rolland, Brian J. Thompson Professor of Optical Engineering.

Schiesser's work is in packaging optics within the boundaries of a next-generation high-power laser in laser fusion energy experiments.

 

Optical design

In sessions on optical design, experienced designers shared lessons learned from previous work, discussed the importance of tolerancing, and described the value in understanding and specifying what is truly needed to achieve the desired performance.

John Rogers of Synopsys, Inc., shared the results of a particularly powerful study demonstrating a typical optimization run to reduce error function can lead to incorrect conclusions since the designer really cares about as-built performance (9633-26). Modifying the optimization scheme to account for this can result in selecting a better design delivering the best overall performance.

Dave Stephenson of Jenoptik Optical Systems LLC described the use of merit functions to enable efficient fabrication of aspheres (9633-27).

The design and production of a 0.5NA micro-field EUV lithography exposure tools for resist development was the topic of the presentation given by Luc Girard of Zygo Corporation (9633-98). The two-mirror design and fabrication of the system achieved excellent results demonstrating a single pass transmitted wavefront error of 0.21nm-0.24nm RMS at the center of the field and 0.48nm RMS at the edge of the 30µm X 200µm field.

 

Food trucks at SPIE Optifab
Popular food trucks provided handy lunch options.

 

Optical materials and coatings

Joel Bagwell of Edmund Optics shared the results of a case study involving the troubleshooting of a recently installed coating system producing parts with excessive variation in index of refraction (9633-35). Gas analyzer results and studies with secondary ion mass spectroscopy provided clues leading the researchers to an error in the installation ductwork material which, when rectified, resolved the problem. The case study demonstrated the sensitivity of these optical components to small variations in the local environment.

 

Fabrication and testing of mirrors

The use of metal optics is important in such fields as astronomy and EUV lithography. Aluminum is a commonly used material in such cases but is not easily polished to sufficient quality for use in the visible and EUV ranges. In his presentation, Jan Kinast of the Fraunhofer Institut für Angewandte Optik und Feinmechanik demonstrated that coating aluminum with a NiP film of 4µm or greater using either an electroless or an electrolytic process can result in polishing performance of 0.2nm RMS. Such performance allows for the possibility of using aluminum into the EUV region (9633-35).

 

SPIE Optifab technical presentations
Fascinating presentations filled the day.

 

Optical engineering

Strategies involving the use of alignment turning for precision positioning of lenses within mounting tubes was discussed by Aleksej Baier of Trioptics GmbH whose colleague, Patrik Langehaneberg, continued along the same theme in describing approaches for active alignment of lenses (9633-36).

The fabrication of metal mirrors suitable for use in a snap-together assembly was described by Matthias Beier of the Fraunhofer Institut für Angewandte Optik und Feinmechanik. Using diamond machining methods and magnetorheological finishing as the fine polishing step, large aperture monolithic freeform shaped mirror modules were fabricated with <0.5nm RMS roughness (9633-37).

 


Here's the latest news

 

Exhibition -- sold out this year!

The exhibition was a busy place all week, according to reports from exhibitors. Among them was Klaus Lassnig, Product Manager of Water Purification/Polishing Powder at Treibacher Industrie AG, a supplier of raw materials for optical manufacturing, who commented on the volume of traffic and the location -- and on seeing the right people at their booths.

"We are seeing new customers and existing customers, too," Lassnig said. "We find that strengthening our relationships with our current customers is very important in this market. Our existing customers give us good referrals to new companies that then become customers. Rochester is the center of precision optical manufacturing in North America. The most influential people in optical manufacturing are at Optifab."

Longtime presenter but first-time exhibitor Mariia Voznesenskaia, CEO of Difrotec OÜ, was among those demonstrating new products. Optifab served as the site of the world debut of their new Difrotec D7 interferometer.

"Optifab is our favorite trade show," said John Meyer of Nanophase Technologies Corp. "I see all my customers including those that are manufacturing companies also exhibiting here."

SPIE Optifab 2015 exhibition
SPIE Optifab 2015 exhibition SPIE Optifab 2015 exhibition
Lovely Warren at SPIE Optifab 2015 exhibition
Rochester Mayor Lovely Warren presided over the exhibition opening on Tuesday
before a tour of the exhibition floor. Above, the mayor chats
with SPIE CEO Eugene Arthurs (center) at one of the more than 180 booths.
SPIE Optifab 2015 exhibition
SPIE Optifab 2015 exhibition SPIE Optifab 2015 exhibition
SPIE Optifab 2015 exhibition SPIE Optifab 2015 exhibition
SPIE Optifab 2015 exhibition SPIE Optifab 2015 exhibition
SPIE Optifab 2015 exhibition
Richard Nastasi, Justin Mahanna, Michael Naselaris
Exhibition chairs are, from left, Richard Nastasi and Justin Mahanna of
Universal Photonics, Inc., and Michael Naselaris of Sydor Optics, Inc.

 

Freeform optics

Presentations on the design, manufacture, and measurement of freeform optics comprised the Wednesday morning sessions.

Kevin Thompson of Synopsys, Inc., discussed the alignment sensitivity of freeform telescopes relative to their traditional unobscured three-mirror astigmat counterparts (9633-41).

Traditional thinking has been that the freeform instruments are more challenging to align; however, this study of comparable telescopes demonstrated that the freeform design was more sensitive for only 2 of the 6 perturbations. Furthermore, that sensitivity could be removed by a single linear compensator based on data from one field point.

SPIE Optifab course program
Courses teaching new skills in a variety of
topics are a vital part of the Optifab week.
SPIE Optifab course program

The importance of full field displays (FFD) in analyzing freeform optics was emphasized by Aaron Bauer of the University of Rochester, who reported on work utilizing a Coddington trace FFD approach (9633-40).

This ray-based approach circumvents some limitations of Zernike FFD's and was extended to studies of coma. The resulting ray-based coma FFD approach allows arc and elliptical coma effects to be viewed independently and was applied to examples including a Cooke triplet and a viewfinder.

Jianing Yao and Di Xu, also of the University of Rochester, reported on the use of Fourier-domain optical coherence tomography (OCT) for use in freeform optics metrology (9633-44). Their design utilized a swept source and an all-reflective pupil scanning configuration. They demonstrated the feasibility of their system by capturing the full profile of an Alvarez surface with a 14.1mm clear aperture and 400µm sag.

 

Diamond turning and molded optics

In the afternoon, Jay Nelson of Edmund Optics shared the results of a case study involving the molding of asphero diffractive surfaces (9633-54).

Initial work with a compression molding process resulted in fractures in all diffractive zones of the optic. The initial corrective action focused on the mismatch of the coefficients of thermal expansion between the optic and the tooling, but experiments centered on this aspect suggested a different root cause was involved.

Subsequent work led investigators to study stress induced during the molding process and corrective actions related to stress relaxation remedied the issue. The case study nicely demonstrates the typical challenges faced by optical manufacturers on production lines.

 

Education for future growth

Panel discussion on strategies for education
Panelists discussed strategies for advanced education to support growth, innovation,
and future jobs, at the end of the conference day on Wednesday.

 

Speaking of jobs ...

SPIE Optifab 2015 Job Fair
Employers looking for candidates to fill current job openings met with interested job-seekers
at the SPIE Job Fair during the exhibition on Wednesday.

 

Outstanding posters

APOMA Outstanding Student Poster awards were presented during Wednesday evening's networking and poster-viewing reception. Winners were:

  • First place, including a $1,000 prize, to Sam Butler and Michael Ricci, University of Rochester, for "Homodyne displacement measuring interferometer probe for optical coordinate measuring machine with tip and tilt sensitivity" (9633-90)
  • Second place, including a $750 prize, to Kameron Tinkham, University of Rochester, for "Cerium oxide polishing slurry reclamation project: characterization techniques and results" (9633-99)
  • Third place, including a $500 prize, to Karine Mathieu, Centre Nationale d'Etudes Spatieles, for "Pixelated filters for spatial imaging" (9633-74).

 


All photos © SPIE, the international society for optics and photonics, except where noted.

SPIE Optifab 2015

12-15 October 2015
Rochester, New York, USA

 


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International Year of Light 2015

 

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