![]() Toshiba had to solve a difficult problem: the same laser had to be able to read signals from two discs with different pit widths. Several possible solutions were considered. Among the candidate solutions are an integrated two-lens switching system which consists of two lenses, one for CD, and the other for DVD, and a dual-focus pickup system in which a single lens is used to achieve focus for both CD and DVD. With the integrated two-lens switching system, two lenses, one for CD and the other for DVD, are switched by rotating the lenses horizontally to read signals for each disc. With the dual-focus pickup system, thanks to the adoption of a hologram lens, a single lens can achieve focus for both CD and DVD without being realigned, and read the signals. |