Signal Analysis of Scratch-Detection on Magnetic Disc by Using Light Reflection Approach

Abstract

In hard disk manufacturing, a process of quality inspection of magnetic disc is crucially focused on finding traces of scratch that occur on the surface by various sources such as production process, machinery, tribology or recording head. It may affect the efficiency of magnetic disc’s read/write ability. Many approaches have been proposed to detect the scratch by either destructive or non-destructive testing. In this study, it shows an analysis of signals from the detected scratches on the magnetic disc by reflection light method, using a CD pick-up head. It works by producing an incidental laser beam to the surface and then detecting it by a photodiode detector. The results showed that when the laser beam is incident onto the magnetic disc with/ without scratch, reflecting lights to the photodiode are different and the signal changes according to the intensity of the incidental/reflecting lights.

Utilization of CD and DVD Pick-Up Heads for Scratch Inspection of Magnetic Disk in Dynamic State Using Microcontroller

“…Therefore, a new technique of low cost, easy process, and scratch detectability has been presented by using ordinary laser doppler and CD pick-up head to inspect surface details because of its advantages on the measurement of object roughness and the identification of scratch location, in a compromising process [8,9]. Moreover, numerous studies have recently shown interesting results of using DVD pick-up head to detect the reflective DNA layers on a DNA chip slide as its potentiality to show the shape of the DNA and count the number of cells [10].…”