ABSTRACT

Requirements of ultra-smooth surfaces have been increasing continuously in the field of optics. Optical materials have been used in many technologies such as telescopes, cameras, astronomical mirrors, metrology, navigation, vision systems, modulation of energy beams (laser, electron, x-rays etc.) and many more. These applications of optics require extreme control over figure

CONTENTS

5.1 Introduction ................................................................................................ 111 5.2 Polishing and Machining Processes ....................................................... 112 5.3 Elastic Emission Machining (EEM) ......................................................... 114 5.4 Mechanism of Material Removal ............................................................ 116 5.5 Force Analysis ............................................................................................ 117 5.6 EEM and Hydrodynamic Lubrication .................................................... 118 5.7 Machining Strategies ................................................................................. 119 5.8 Shear Stress in EEM ................................................................................... 121 5.9 Effect of Tool Roughness........................................................................... 124 5.10 Types of Tool, Workpiece and Abrasive Interactions............................ 125

5.10.1 Semi-Contact Case ......................................................................... 125 5.10.2 Non-Contact Case .......................................................................... 126

5.11 Factors Affecting Shear Stress ................................................................. 126 5.12 Process Environment................................................................................. 127 5.13 Agglomerated and Separated Abrasive Particles .................................. 128 5.14 Applications ................................................................................................ 128

5.14.1 Optics for Extreme Ultraviolet Lithography .............................. 128 5.14.2 Ellipsoidal Mirrors in X-Ray Microscopy ................................... 128 5.14.3 Focusing Mirrors in SR Beamlines .............................................. 129

5.15 Remarks ....................................................................................................... 129 References ............................................................................................................. 130

(profile) and surface roughness. Apart from the figure and surface roughness control, fabrication of stress-free surfaces is equally important to reduce the probability of unexpected failure of optical materials. Very few processes are available to process optical materials when the requirement is of figure accuracy in the sub-micron level and surface roughness in the angstrom level. One such process is ‘elastic emission machining (EEM)’.