Holographic representation: Hologram plane vs. object plane

Abstract

Digital holography allows the recording, storage and subsequent reconstruction of both amplitude and phase of the light field scattered by an object. This is accomplished by recording interference patterns that preserve the properties of the original object field essential for 3D visualization, the so-called holograms. Digital holography refers to the acquisition of holograms with a digital sensor, typically a CCD or a CMOS camera, and to the reconstruction of the 3D object field using numerical methods. In the current work, the different representations of digital holographic information in the hologram and in the object planes are studied. The coding performance of the different complex field representations, notably Amplitude-Phase and Real-Imaginary, in both the hologram plane and the object plane, is assessed using both computer generated and experimental holograms. The HEVC intra main coding profile is used for the compression of the different representations in both planes, either for experimental holograms or computer generated holograms. The HEVC intra compression in the object plane outperforms encoding in the hologram plane. Furthermore, encoding computer generated holograms in the object plane has a larger benefit than the same encoding over the experimental holograms. This difference was expected, since experimental holograms are affected by a larger negative influence of speckle noise, resulting in a loss of compression efficiency. This work emphasizes the possibility of holographic coding on the object plane, instead of the common encoding in the hologram plane approach. Moreover, this possibility allows direct visualization of the Object Plane Amplitude in a regular 2D display without any transformation methods. The complementary phase information can easily be used to render 3D features such as depth map, multi-view or even holographic interference patterns for further 3D visualization depending on the display technology.

JPEG Pleno: Providing representation interoperability for holographic applications and devices

“…Bernardo et al. studied the impact of encoding the field at different depths. In particular, in the case of a single object, the benefit of performing coding in the reconstruction plane, ie object plane is discussed .…”

“…Some of them were computed from 3D videos of real‐existing scenes. Several bit depths, resolutions, and pixel pitches are offered, enabling a wide range of testing conditions. EmergImg‐HoloGrail database This database has several holograms obtained with a Mach‐Zehnder interferometer setup . It is one of the larger databases of acquired holograms.…”

“…For example, phase wrapping might result in large error measurements, while the effective errors might be extremely small. Overall, applying these metrics on an amplitude‐phase representation was found to deliver less accurate results compared to deploying them on Cartesian, that is, real‐imagery representations .…”

“…The resulting basis functions allow the data with respect to the scene depth to be analyzed, and have been encoded with SPIHT [37]. Bernardo et al [38] studied the impact of encoding the field at different depths. In particular, in the case of a single object, the benefit of performing coding in the reconstruction plane, ie object plane is discussed [39].…”

“…For example, phase wrapping might result in large error measurements, while the effective errors might be extremely small. Overall, applying these metrics on an amplitude- phase representation was found to deliver less accurate results compared to deploying them on Cartesian, that is, real-imagery representations [38]. Ahar et al [50] recently presented a versatile similarity measure that attempts to resolve this caveat by proposing a multifactor measure (considering the factors accounting for amplitude, phase and sign differences) while 'annealing' incidental phase wraps.…”