Method for recording holograms that form a speckle-free image of the aiming mark in holographic collimator sights and other similar augmented-reality devices

S. N. Koreshev and S. O. Starovoitov, "Method for recording holograms that form a speckle-free image of the aiming mark in holographic collimator sights and other similar augmented-reality devices," Journal of Optical Technology. 89(4), 225-228 (2022). https://doi.org/10.1364/JOT.89.000225

Subject of study. A method for recording holograms that form a speckle-free image of the aiming mark in holographic collimator sights and other similar augmented-reality devices is proposed. Method. The method does not require matte glass to fill the exit pupil of the sight. It is based on a property of the Fourier transform referred to as the shift theorem. According to this theorem, the image reconstructed using a Fourier hologram recorded by a plane reference wave stays stationary when the hologram is moved. Main results. A two-stage practical implementation of the method is proposed. An auxiliary hologram comprising a two-dimensional matrix of equidistantly positioned holograms of the aiming mark spectrum is recorded in the first stage. Its total size is equal to the required size of the exit pupil of the sight. A hologram for the sight is recorded in the second stage using an image formed by the entire aperture of the auxiliary hologram. Requirements posed on the geometric parameters of the recording and reconstruction schemes of the principal and auxiliary holograms are presented and justified. The possibility of practical implementation of the method and its effectiveness are experimentally confirmed by fabrication of a hologram forming an aiming mark image within a pupil with dimensions of 84×42mm². Practical significance. The method for recording holograms that form a speckle-free image of the aiming mark in holographic collimator sights and other similar augmented-reality devices proposed in this study allows the sharpness of the aiming mark image observed in the sight to be increased, i.e., makes it more convenient for observation. The use of this method slightly complicates the fabrication of the hologram for the sight, and thus increases its cost, albeit insignificantly.