KEYWORDS: Holograms, Holographic displays, Spatial light modulators, RGB color model, Near eye displays, 3D image reconstruction, Multiplexing, Light sources and illumination, Lenses, 3D displays
Near-eye displays (NED) are devices that are intended to project three dimensional images with wide-angle view. However, at present most of the 3D displays are based on stereoscopic principle, which does not satisfy the required parameters of human vision. This limitation can be overcome by implementing digital holograms within the NED. This is because a digital hologram contains the whole wavefront information of the scene. Thus, a holographic NED (HNED) is capable to reconstruct any three-dimensional scene while matching all the physiological cues of human vision. Nevertheless, truly immersion experience in HNED requires wide angle view and full colour reconstruction as well. In this work, we study HNED for pupil and non-pupil configuration that reconstructs large 3D colour scenes. The colour reconstruction is made by using RGB illumination and time multiplexing. Numerical analysis is carried out to test the FOV and the quality of reconstructions. Moreover, experimental colour reconstructions are made by employing laser for the pupil configuration and LED for non-pupil configuration. This is done to compare reconstruction quality and FOV of the displayed 3D scene.
Fourier lensless holograms of large size and large viewing angle are investigated. The investigated hologram is non paraxial and has large size in horizontal direction and small in the vertical one. This paper focuses on the problem of efficiency and quality of numerical reconstruction of such large holograms. Three wavefront propagation methods are analyzed for this task: (i) Fresnel propagation, (ii) classical Angular Spectrum and (iii) Angular Spectrum with optimized zero padding. All the numerical approaches are investigated theoretically and experimentally for its numerical efficiency and reconstruction errors. Experimental verification is provided.
The quality of an optical system forming a laser beam can be characterized through the measurement of aberrations in a deformed wavefront. The wavefront can be evaluated interferometrically in lateral shearing interferometer in which a coherent wavefront under test interferes with a laterally sheared wavefront copy. The resulted fringe pattern contain information on the first derivative of wavefront shape, according to direction of the shear. In this contribution we discuss the challenge related to wavefront shape reconstruction based on two lateral shearing interferograms from orthogonal shear directions. In case of not complicated wavefront the directional phase integration can be applied. Proposed method of reconstruction entirely omits this complicated process. It is based on calculations of the coefficients of Zernike polynomials from derivatives of wavefront shape and they are used for wavefront shape reconstruction. The utility of the proposed approach is tested numerically and demonstrated with characterization of aberrated wavefronts. Moreover, the simple configuration of lateral shear interferometer with two separated lateral shearing direction is introduced with context of monitoring of high power laser beam. At the end of the data analysis we apply an method for extracting the Zernike coefficients. The accuracy of implemented method is verified by characterization of generated spherical and highly aberrated wavefront. An error analysis indicates optimal conditions of measurements and proves high accuracy of developed method.
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