Optical recording and reading system, optical data storage medium and use of such medium

摘要

An optical recording and reading system for use with an optical data storage medium ( 5 ) is described. The system comprises the medium ( 5 ) having a recording stack ( 9 ), formed on a substrate ( 8 ). The recording stack ( 9 ) is suitable for recording by means of a focused radiation beam ( 1 ) with a wavelength lambda in air. The recording stack ( 9 ) has a first optical surface ( 6 ) most remote from the substrate ( 8 ). An optical head ( 3 ), with an objective ( 2 ) having a numerical aperture NA>0.8 and from which objective ( 2 ) the focused radiation beam emanates ( 1 ) during recording, is ( 2 ) arranged on the recording stack ( 9 ) side of said optical data storage medium ( 5 ). The objective has a second optical surface ( 7 ) closest to the recording stack ( 9 ), and is adapted for recording/reading at a free working distance d_F of smaller than 50 mum from the first optical surface ( 6 ). At least one of the first optical surface ( 6 ) and the second optical surface ( 7 ) is provided with a transparent hydrophobic layer ( 10 ) that has a refractive index n and has a thickness smaller than 0.5 vn. In this way reliable recording and reading is achieved, specifically contamination build-up on the second optical surface ( 7 ) is prevented or counteracted.