Three-dimensional integral imaging based capture and display system using digital programmable Fresnel lenslet arrays

Ankara : The Department of Electrical and Electronics Engineering and the Graduate School of Engineering and Science of Bilkent University, 2012.Thesis (Ph. D.) -- Bilkent University, 2012.Includes bibliographical refences.A Fresnel lenslet array pattern is written on a phase-only LCoS spatial light modulator device (SLM) to replace the regular analog lenslet array in a conventional integral imaging system. We theoretically analyze the capture part of the proposed system based on Fresnel wave propagation formulation. Due to pixelation and quantization of the lenslet array pattern, higher diffraction orders and multiple focal points emerge. Because of the multiple focal planes introduced by the discrete lenslets, multiple image planes are observed. The use of discrete lenslet arrays also causes some other artefacts on the recorded elemental images. The results reduce to those available in the literature when the effects introduced by the discrete nature of the lenslets are omitted. We performed simulations of the capture part. It is possible to obtain the elemental images with an acceptable visual quality. We also constructed an optical integral imaging system with both capture and display parts using the proposed discrete Fresnel lenslet array written on a SLM. Optical results, when self-luminous objects, such as an LED array, are used indicate that the proposed system yields satisfactory results. The resulting system consisting of digital lenslet arrays offers a flexible integral imaging system. Thus, to increase the visual performance of the system, previously available analog solutions can now be implemented digitally by using electro-optical devices. We also propose a method and present applications of this method that converts a diffraction pattern into an elemental image set in order to display them on a display-only integral imaging setup. We generate elemental images based on diffraction calculations as an alternative to commonly used ray tracing methods. Ray tracing methods do not accommodate the interference and diffraction phenomena. Our proposed method enables us to obtain elemental images from a holographic recording of a 3D object/scene. The diffraction pattern can be either numerically generated or digitally acquired from optical input. The method shows the connection between a hologram (diffraction pattern) of a 3D object and an elemental image set of the same 3D object. We obtained optical reconstructions with a display-only integral imaging setup where we used a digital lenslet array. We also obtained numerical reconstructions, again by using the diffraction calculations, for comparison. The digital and optical reconstruction results are in good agreement. Finally, we showed a method to obtain an orthoscopic image of a 3D object. We converted an elemental image set that gives real pseudoscopic reconstruction into another elemental image set that gives real orthoscopic reconstruction. Again, we used wave propagation simulations for this purpose. We also demonstrated numerical and optical reconstructions from the obtained elemental image sets for comparison. The results are satisfactory given the physical limitations of the display system.Yöntem, Ali ÖzgürPh.D

Demonstrating a multi-primary high dynamic range display system for vision experiments.

We describe the design, construction, calibration, and characterization of a multi-primary high dynamic range (MPHDR) display system for use in vision research. The MPHDR display is the first system to our knowledge to allowfor spatially controllable, high dynamic range stimulus generation using multiple primaries.We demonstrate the high luminance, high dynamic range, and wide color gamut output of the MPHDR display. During characterization, the MPHDR display achieved a maximum luminance of 3200 cd=m2, a maximum contrast range of 3; 240; 000 V 1, and an expanded color gamut tailored to dedicated vision research tasks that spans beyond traditional sRGB displays. We discuss how the MPHDR display could be optimized for psychophysical experiments with photoreceptor isolating stimuli achieved through the method of silent substitution. We present an example case of a range of metameric pairs of melanopsin isolating stimuli across different luminance levels, from an available melanopsin contrast of117%at 75 cd=m2 to a melanopsin contrast of23%at 2000 cd=m2

Demonstrating a multi-primary high dynamic range display system for vision experiments.

We describe the design, construction, calibration, and characterization of a multi-primary high dynamic range (MPHDR) display system for use in vision research. The MPHDR display is the first system to our knowledge to allowfor spatially controllable, high dynamic range stimulus generation using multiple primaries.We demonstrate the high luminance, high dynamic range, and wide color gamut output of the MPHDR display. During characterization, the MPHDR display achieved a maximum luminance of 3200 cd=m2, a maximum contrast range of 3; 240; 000 V 1, and an expanded color gamut tailored to dedicated vision research tasks that spans beyond traditional sRGB displays. We discuss how the MPHDR display could be optimized for psychophysical experiments with photoreceptor isolating stimuli achieved through the method of silent substitution. We present an example case of a range of metameric pairs of melanopsin isolating stimuli across different luminance levels, from an available melanopsin contrast of117%at 75 cd=m2 to a melanopsin contrast of23%at 2000 cd=m2

Perception of perspective in augmented reality head-up displays

Augmented Reality (AR) is emerging fast with a wide range of applications, including automotive AR Head-Up Displays (AR HUD). As a result, there is a growing need to understand human perception of depth in AR. Here, we discuss two user studies on depth perception, in particular on the perspective cue. The first experiment compares the perception of the perspective depth cue (1) in the physical world, (2) on a flat-screen, and (3) on an AR HUD. Our AR HUD setup provided a two-dimensional vertically oriented virtual image projected at a fixed distance. In each setting, participants were asked to estimate the size of a perspective angle. We found that the perception of angle sizes on AR HUD differs from perception in the physical world, but not from a flat-screen. The underestimation of the physical world's angle size compared to the AR HUD and screen setup might explain the egocentric depth underestimation phenomenon in virtual environments. In the second experiment, we compared perception for different graphical representations of angles that are relevant for practical applications. Graphical alterations of angles displayed on a screen resulted in more variation between individuals' angle size estimations. Furthermore, the majority of the participants tended to underestimate the observed angle size in most conditions. Our results suggest that perspective angles on a vertically oriented fixed-depth AR HUD display mimic more accurately the perception of a screen, rather than the perception of the physical 3D environment. On-screen graphical alteration does not help to improve the underestimation in the majority of cases