Coded aperture correlation holography–a new type of incoherent digital holograms

Abstract

We propose and demonstrate a new concept of incoherent digital holography termed coded aperture correlation holography (COACH). In COACH, the hologram of an object is formed by the interference of light diffracted from the object, with light diffracted from the same object, but that passes through a coded phase mask (CPM). Another hologram is recorded for a point object, under identical conditions and with the same CPM. This hologram is called the point spread function (PSF) hologram. The reconstructed image is obtained by correlating the object hologram with the PSF hologram. The image reconstruction of multiplane object using COACH was compared with that of other equivalent imaging systems, and has been found to possess a higher axial resolution compared to Fresnel incoherent correlation holography.

Incoherent Digital Holography: A Review

“…As a method advancing from FINCH, a remarkable single-path incoherent DH has been recently proposed, called coded aperture correlation holography (COACH) [80]. An optical setup initially proposed for COACH is the same as that of FINCH, as illustrated in Figure 4.…”

“…To improve the depth resolution, one should make the spatial frequency distribution of CPM uniform. With COACH, incoherent 3D imaging [80] and incoherent color 3D imaging with a diffractive lens [81] have been demonstrated. It is worth noting that a diffractive lens is not needed to separate wavelength information by using a holographic technique [67,82].…”

Choice of optical system is critical for the security of double random phase encryption systems

“…It is known that in optical encryption system, diffracted light from the object passes through one another and thus can additionally be combined in novel passive multiplexing schemes. Typically, such optical security systems require the modulation and capture of the full complex encrypted field information, i.e., both the intensity and the phase, involving for example digital holographic (DH) and interferometric techniques [32][33][34][35]. In following, we briefly review the fundamental optical encryption methods.…”

“…As it can be seen, it involves multiplication of the diffracted input light field by random phase masks or keys (RPMs) placed both in the input (space) and the Fourier (spatial frequency) domains. We note that RPMs can be implemented using, for example, ground glass, optical diffusers or suitable modulated spatial light modulator (SLM) [35]. , ) and , ) , ) respectively, are used to encrypt the 2D image.…”

Multispectral hyperbolic incoherent holography

“…Various types of techniques have proposed. One technique is based on diffraction theory which can be implemented by making use of spatial light modulator [3][4][5] or concave mirror [6] and other technique uses radial shearing [7] or rotational shearing [8] interferometric systems.…”