Gradient-index rod lens with a high acceptance angle for color use by Na+ for Li+ exchange

The relationship between the characteristics of gradient-index rod lenses obtained by ion exchange and their mother glass compositions is studied. It is observed that [Li.sub.2]O content, [R.sub.2]O ([Li.sub.2]O + [Na.sub.2]O) content, and the [Li.sub.2]O/[Na.sub.2]O ratio are important factors in attaining a high acceptance angle and a small field curvature. Thus the gradient-index lens array is fabricated by the use of a newly developed glass composition and its optical performance; the modulation transfer function, luminous intensity, and chromatic aberration are precisely evaluated. The array is found to have a sufficiently high performance to be applicable for color use. Key words: Gradient-index, Li-containing glass, ion exchange, acceptance angle, field curvature, chromatic aberration.