Optical system and device using the same

摘要

The invention relates to a viewing and an image pickup optical system for display devices, which can be used with high efficiency at a plurality of wavelengths and enables bright images to be viewed with satisfactory color reproducibility. The optical system comprises a first prism 3, a second prism 4 and a volume hologram element 6 disposed between them and cemented to them. The hologram element 6 comprises a first grating vector corresponding to at least a first wavelength and a second grating vector corresponding to a second wavelength shorter than the first wavelength. As the light beam comprising the first and second wavelengths passes through the hologram element 6, the component of the first wavelength transmits at a given angle of incidence in a region between a first lambdtheta continuous curved region in which the diffraction efficiency is 10% or greater as determined form the first grating vector and a second lambdtheta continuous curved region in which the diffraction efficiency is 10% or greater as determined from the second grating vector, and the component of the second wavelength transmits at a given angle of incidence in a region on a shorter wavelength side with respect to the 2 lambdtheta continuous curved region.