Foreign citizens can obtain a China visa from:
It is recommended that attendees traveling to the meeting apply for Tourist (L) Visa instead of the Non-Business (F) Visa. An embassy may require additional documents for an F visa that SPIE or the host organization are unable to provide. The invitation letter provided by SPIE on behalf of the host organization should be sufficient for the requirements of an L Visa.
To request an invitation letter for your visa application, submit a Visa Invitation Letter Request Form as soon as possible. SPIE will stop issuing invitation letters 2 weeks before the event.
Resources:
Most international travelers will need a Chinese visa to enter the country.