Diffraction optical elements with broadband and large incident angles

TL;DR: In this paper, a manufacturing method that glued two diffractive optical elements together to reduce the stray light scattered into unwanted diffraction orders was presented, which enabled the system to realize a diffraction efficiency over 90% when the incident angle is no more than 54°.

Abstract: Diffraction efficiency is a key assessment criterion for the hybrid diffractive-refractive optical systems with a wide field of view. However, diffractive optical elements cannot obtain high diffraction efficiency simultaneously in the case of broad wavelength band and large incident angle range. This character limits the applications of DOEs in the optical systems with large field of view and wide working wavelength range. In this paper, we present a manufacturing method that glued two diffractive optical elements together to reduce the stray light scattered into unwanted diffraction orders. Firstly, the separated DOEs are fabricated with the ultra-precision turning method. Then, through chosen suitable optical adhesives to glue those separated DOEs. Based on the principle of maximum diffraction efficiency on the design waveband and incident angles, we optimized the parameters of the diffractive optical elements to achieve broadband high diffraction efficiency and modulation transfer function over a wide incident angle range. The DOEs enable the system to realize a diffraction efficiency over 90% when the incident angle is no more than 54°. This method is easy to realize and maintain high structural stability. We can give a more precious design than presented methods, such as substrate optical material section and optical adhesives section. The benefit of this design and manufacturing method is that the maximum integral diffraction efficiency overall the wide angles of incidence in the whole waveband can be achieved, thereby ensuring the high modulation transfer function of a hybrid imaging optical systems with diffractive elements.