Application of low-birefringence polystyrene in high-resolution imaging-lens systems

Polystyrene (PS) has not been much used as an optical material due to the considerably high birefringence of PS. For the extensive use of PS in the imaging-lens systems, lower birefringence should be attained for the enhancement of the resolution. Previously, we have developed PS with extremely low birefringence (LB-PS) even when the molecular chain orientation of PS occurred. It indicates that PS may now become an effective material with excellent properties for optical lenses. In this paper, we compared the birefringence of our developed LB-PS with ones of commercial optical polymers that are most commonly utilized in imaging-lens systems. It was confirmed that the birefringence of LB-PS was comparable or even better than that of the commercial ones with high resolution. By designing an imaging-lens system, it was also confirmed that employing PS with the Abbe number of 31.5 could be highly effective in compensating for chromatic aberration as well as obtaining high optical resolution. Moreover, the resolution performance of several lens systems was calculated, analyzed, and compared by considering the birefringence of cyclo-olefin polymer (COP), normal PS, and LB-PS. It was found that LB-PS could maintain high resolution, while normal PS with high birefringence exhibited significant decrease in resolution. It was also found that LB-PS generated higher resolution than COP. All these results revealed that LB-PS could be an excellent optical material to compensate for the chromatic aberration of lens systems, leading to the enhancement of the actual resolution performance. It was, therefore, expected that LB-PS could contribute to improving the resolution performance of smartphone cameras and security cameras.