SDSS (Sloan Digital Sky Survey) photometric system is the most common and
important in modern astronomy. The large volume of survey data observed by
the SDSS project became the cultural legacy. Broad band filters currently installed
in the wide field camera (e.g. DECam) were designed on the basis of the SDSS
photometric system.

Asahi provided the world's first SDSS u, g, r, i, z-band filter set to Apache Points
Observatory in New Mexico, USA thirty years ago. The original SDSS filters were
produced by the combination of colored glass and interference coatings.

Nowadays new SDSS filters with higher efficiency are much more preferred, even if
the bluer slope in passband is not similar to the slope of colored glass.
We succeeded in making the higher transmission and flat passband by all dielectric
coating design and our proprietary magnetron sputtering technology.