“…DataPlay and LG made cartridge-type SFFO disks, with disk diameter (') = 32 mm, numerical aperture ðNAÞ ¼ 0:72, and wavelength () = 650 nm, and ' ¼ 27:4 mm, NA ¼ 0:85, and ¼ 660 nm, respectively. 1,2) The disk cartridge is used mainly for dust protection, but it causes a rise in manufacturing cost and an increase in the thickness of the SFFO drive deck. Recently, Philips reported that for the CFII-type SFFO drive (5 Â 43 Â 63 mm 3 ) and media, they chose a blue laser system (NA ¼ 0:85, ¼ 405 nm) and a cartridge-free disk.…”