Investigation of the general design principle of a single lens and the development of a new NA=0.85 single lens

An aspherical single lens is widely used as an objective lens for optical discs. These lenses are designed as aplanats or are very close to an aplanat design. We have analyzed the lens with NA of 0.85 and determined general equations that predict paraxial parameters of such lenses. The equations are very useful for determining lens specifications. Applying the equations we have determined the specifications of a new lens whose focal length is 2 mm. The wavefront aberration was 24 mlambda. and well below the diffraction limit. The experimental results on an optical pickup with a 405 nm LD are also shown. The jitter value of the read-back signal using a 23.3 Gbytes phase change disk was as small as 9.0%. This jitter value is sufficient for achieving a low error rate after decoding.