Usage case example details

Optical Coatings Japan produced a large-diameter filter for use on the Hyper Suprime-Cam (HSC).
The Subaru Telescope is located on the summit of Mauna Kea in Hawaii. It is a large infrared telescope with a diameter of 8.2 m and is operated by the National Astronomical Observatory of Japan, one of the National Institutes of Natural Sciences. The HSC is one of the observational instruments of the Subaru Telescope. It is an ultra-wide-field digital camera with 116 CCD elements and approximately 870 million pixels. It is 3 m high and weighs 3 t, and can capture an area as large as nine full moons in one photograph. Various projects are in progress, including an investigation of the distribution of dark matter using the weak gravitational lensing effect and the observation of distant galaxies.

The size of the filter on the HSC is a diameter of 600 mm. With such a large diameter filter, it was necessary to coat the filter evenly so that the spectral characteristics are uniform at every point on the filter surface. This made the manufacturing very difficult and it required a whole year of development work. In order to perform the coating with no unevenness, we repeatedly adjusted the film formation conditions and increased the accuracy of the film formation distribution reproducibility to become able to accurately control the film thickness.In addition to a narrow band pass filter, the Subaru Telescope also uses our r-band standard filter and window for the CCD dewar. Our experience manufacturing the large-diameter filter for the HSC has led to our current high level of film formation technology. Optical Coatings Japan will continue working to make a contribution in astronomy and all other fields of research by supplying highly accurate filters that satisfy the requirements.