| 摘要 |
PURPOSE:To measure a gap of down of <=0.1mum by using white light by providing a groove whose bottom part slants in parts of the reverse surface of an optical head from its one end to the other end. CONSTITUTION:The groove 11 is formed in the reverse surface 1a of the optical head 1 and the bottom part 11a of the groove 11 slants to a flexible disk 2. When light 3 with single wavelength is projected from the top surface 1b of the head 1, part of it is reflected 3a' by the bottom part 11a and light transmitted through the head 1 is reflected 3b by the surface of the disk 2. Here, when the wavelength of the light 3 in use is denoted as lambda, interference fringes are formed on condition that the interval between the bottom part 11a and the surface of the disk 2 is >=lambda/4. Therefore, even when the gap between the reverse surface 1a of the head 1, e.g. slide surfaces 10a and 10b and the surface of the disk 2 is <=lambda/4, it is measured sufficiently and the fine gap of <=0.1mum can be measured.
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