Total internal reflection diffraction gratings in conical mounting, where the plane of incidence does not contain the grating vector, are investigated in this paper and the relevant conditions and parameters for such gratings are presented. These are then used to design total internal reflection diffraction gratings in conical mounting that the diffraction angle into the first order is equal to the incidence angle. The applications of such gratings in conical mounting to planar optics configurations, which have at least three gratings and one of them is total internal reflection diffraction grating in conical mounting, are discussed in detail. Also, the diffraction properties of all three gratings in this configuration, especially the grating period which is the most important parameter of gratings, are analyzed. The main condition, on which all the gratings in planar display configuration have the same grating periods, is presented based on theoretical analysis: the turning grating should be in 60 deg conical mounting. The configuration can be used to virtual display or wearable display.
Holograms recorded in dichromated gelatin (DCG) are usually sealed with a glass plate cemented with an epoxy glue to protect the holograms from moisture in the environment. An investigation of the wavelength properties of sealed DCG holograms had been carried out paying attention to holograms which were exposed to different temperature and humidity environment in this work. The investigation had revealed that (a) exposing the sealed DCG holograms to high relative humidity (RH=98%) environment or immersing them in room-temperature water for 20 hours can not affect the holograms; (b) the sealed DCG holograms can be used at temperature below 50°C without showing undue detrimental effects regarding their optical properties; (c) the peak wavelength of sealed DCG holograms can cause blue shift of several nanometers at 70°C~85°C and the velocity of blue shift is proportional to the environmental temperature; (d) the holograms can be destroyed at 100° or above. The experimental results above will be analyzed and discussed in this paper. A method to improve the stability of sealed DCG holograms is proposed: baking the sealed DCG holograms at proper temperature (e.g., 85°C in this study).