| 摘要 |
PURPOSE:To measure a distance equal to or less than the half-wavelength of measuring light, by using interference fringe of light which is incident from one surface of a transparent substrate and reflected from the surface of matter opposed to the transparent membrane provided to the other surface of said substrate and light reflected from the other surface of the transparent substrate. CONSTITUTION:Alumina (refractive index kF=1.768) is applied to a transparent substrate made of quartz glass in the thickness t=0.433mum to form a transparent membrane 8 to constitute a false magnetic disc 9. When measuring light emitted from a light source 3 is sodium D rays (wavelength lambda=0.5893mum) and the distance ST between the surface D of the disc 9 and the surface F of a magnetic head 2 is represented by formula (1), interference fringe l due to measuring lights reflected from the surface F and the surface D is observed by a monitor 6. The gap S of the disc 9 and the head 2 is represented by formula (2). When the wavelength of measuring light is set to 0.5893mum or less while the thickness of the transparent membrane 8 is set to 0.433mum or more, the distance S of 0.05mum or less can be measured. |
