An optical lever approach to photodetector measurements of the pickup-head flying height in an optical disk drive

Abstract

In order to increase the storage capacity and the density of near-field optical disk drives, a flying pickup-head has to allow a slider to fly at a stable height above the disk surface with the use of near-field optics. Since both the precision of the track pitch and the flying height are of a nanometre scale, it is necessary to increase the motion accuracy of the pickup-head. In this study, a piezoelectric bender is used as an actuator of the pickup-head, and two quadrant photodetectors are used to sense the pickup-head displacement and the rotating disk deformation. Based on an optical lever method that magnifies a small displacement, the flying height variation of the pickup-head above the disk is measured. Further results show that using the proposed measurement method in the real-time control of flying height is feasible.

Organic Ultraviolet Photodetectors Exhibiting Photomultiplication, Low Dark Current, and High Stability

“…Photodetectors have a wide range of applications, from disk drives and motion sensors to environmental monitoring and industrial process control. [2a‐d] The central figures of merit for photodetectors are typically responsivity ( R ), noise equivalent power, and specific detectivity ( D* ), which can both be optimized by maximizing external quantum efficiency (EQE) while maintaining a low dark current. Organic photodetectors have undergone steady improvement since their introduction, one of the most significant steps being the incorporation of a bulk heterojunction (BHJ) morphology, which allows more effective charge transport in the active layer.…”

Spatial Multiplexing Technique for Improving Dynamic Range of Speckle Correlation based Optical Lever

“…In 1826, Poggendorf invented the Optical Lever (OptLev) for improving the sensitivity of theodolites to an accuracy of 5 seconds of an arc and later, it was used by Gauss, Weber, Ising, Mol, and Burger for improving the accuracy of the measurements in their respective experiments 1 . Today, OptLev is widely used for sensing angular variations of a mirror under observation with a high accuracy 2–9 . In some cases, OptLev is also used for the amplification of small displacements 10 .…”

Design and Characterization of a Birefringent-Type Compact Displacement Sensor for Improving Measurement Sensitivity by a Guided-Wave Beam

“…PSD-based beam displacement measurements are important for various uses, including the atomic force microscope, the proximity exposure tool, the optical pickup head, and the Goos-Hänchen effect [2][3][4][5]. Incidentally, phase-interrogation due to optical length differences between the reference and sensing paths was proposed for displacement measurements in various interferometers [6,7].…”