Tokai lens coating technology helping space exploration

Tokai Optical’s light condenser attached to a large-diameter telescope. Photo: Cherenkov Telescope Array

Japanese ophthalmic lens company Tokai Optical has supplied a light concentrator to support space exploration at the University of Tokyo’s Institute for Cosmic Ray Research.

Installed in the institute’s first astronomical observatory, Tokai’s light concentrator will be attached to a large-diameter telescope used in the Cherenkov Telescope Array (CTA) project, one of the world’s largest gamma-ray observatories.

An international joint project involving 31 countries, CTA is observing cosmic gamma rays by capturing Cherenkov radiation emitted when energy-rich gamma rays from outer space collide with the earth’s atmosphere.

“The light concentrator Tokai developed comprises a group of stereoscopic mirrors, an aggregation of about 2000 mirrors, each about 2.5m in diameter, and is designed to effectively concentrate Cherenkov radiation with a wavelength of 300 to 500nm,” the lens company said.

“It captures Cherenkov radiation reflected by parabolic reflectors using photodetectors. The high-precision thin films are essential for the excellent reflectance required in this light concentrator.”

Scientists have established that gamma-rays have the smallest wavelengths and the most energy of any wave in the electromagnetic spectrum.

“Unlike optical light and x-rays, gamma-rays cannot be captured and reflected by normal mirrors. Gamma-ray wavelengths are so short that they can pass through the space within the atoms of a detector,” the lens company explained.

Tokai said it was proud of its plastic forming and coating technology, which is unique for an ophthalmic lens manufacturer.

“The plastic has a nanometer-order surface finish which is very smooth, and multilayer films (enhanced aluminum mirrors) consisting of metal and dielectrics generated by vacuum deposition are formed to realize high-efficient light concentrators. At the same time, Tokai uses its advanced technology to produce the most premium coating for its ophthalmic lenses.”

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