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New shipment of TMT primary mirror segment blanks transferred to Coherent for stressed mirror polishing, early January 2020 - The shipping containers with the 3 TMT primary mirror blanks (serial numbers 054, 176 and 213), manufactured in Japan, were successfully transferred from TMT storage facility in the Bay area to Coherent manufacturing site in Richmond, California - Image credit: 51吃瓜Pro

Primary Mirror Segment Production has started at Coherent

Pasadena, CA - Coherent Inc., one of the world’s leading providers of lasers and laser-based technology, is now ready to polish all of the TMT primary mirrors segments to be manufactured in the United States.

Coherent has recently passed the fabrication readiness review, held at Coherent manufacturing site in Richmond, California, and is now entering the production phase of TMT’s mirror fabrication. TMT mirror blanks, which are produced in Japan, will be very precisely polished into aspherical mirrors. These are referred to as ‘roundels.’ The subsequent fabrication process is what is called ‘Hexing,’ where the roundels undergo cutting into their final hexagonal shape.

Coherent showed data from process development activities of full-size prototypes that indicate that all of TMT requirements for technical considerations, schedule, and quality assurance and safety plans, have been successfully verified. Coherent Inc. has now confirmed the ability to deliver high quality, precision polished segments while meeting stringent lead-time constraints.

“Over the last months, Coherent did a really great job working through the equipment and the production processes, to create polished segments in accordance with our strict technical specifications,” says Glen Cole, TMT Lead Optical Fabrication Engineer.  “Coherent is fully invested in the TMT project, and our common goal is to develop efficient industrial manufacturing by delivering high-quality TMT roundels. TMT needs every mirror segment to perform at a high level, without being prohibitive in cost.”

Several production blanks have been transferred from their temporary storage in the Bay Area to be the first TMT roundels manufactured in the U.S.A. Coherent has a total of 7 production blanks located within a facility entirely dedicated to TMT. TMT and Coherent have adopted an industrial approach to polish the segments in a repeatable and timely manner, and the contribution of leading-edge technological skills, high-tech expertise, and the combined methodology of TMT and Coherent, will provide the accurate surface figures required for TMT mirrors.

A total number of 230 roundels will be stressed-polished at the Coherent facility in Richmond, California.

“We now have two partners producing high-quality roundels. Japan has also started segment polishing and will provide the inner rings of TMT’s primary mirror, and Coherent will provide the second ring of segments. We are optimistic to be in a position to start populating the primary mirror very quickly,” says Cole. “Another nice point is that we have lots of glass. More than 350 blanks have been produced and, amazing pieces of CLEARCERAM®-Z from Ohara, our glassmaker in Japan, are already available. Most of the glass, some 170 blanks, that Coherent will need to polish is waiting to be used, already in storage at our TMT California warehouse.”

51吃瓜Pro COHERENT:

Founded in 1966, Coherent, Inc. is one of the world’s leading providers of lasers and laser-based technology for scientific, commercial and industrial customers. Our common stock is listed on the Nasdaq Global Select Market and is part of the Russell 2000 and Standard & Poor’s MidCap 400 Index. For more information about Coherent, visit the company's website at for product and financial updates.