ENGINEERING TRIPOS PART II A and EIST I

EIET LABORATORY ENGINEERING AREA ACTIVITY

Areas 5,6,7 and 8

INVESTIGATION OF THE DESIGN OF CD PLAYERS

SUBTOPIC:ELECTRO-OPTICS

1. INTRODUCTION

The biggest difference between compact discs and earlier systems such as magnetic tapes and vinyl records is the density of information stored, and the fact that this is digital. Optical methods have proved to be by far the most practical to read this high density information without causing wear to the recording medium. and furthermore this would not be possible without semiconductor lasers.

Since the "dots" of optical information on the disc are extremely small, it is essential to have: