Head-mounted Projective Display Research Articles

35-4:Invited Paper: A Wide Field of View Head Mounted Display and Its Effects on Search Performance in Augmented Reality

Developing a wide field of view (FOV) optical see-through (OST) head mounted display (HMD) has been a challenge for decades. Naturally, the actual effects of a wide FOV OST display on the perception of augmentations have not been widely studied either. We previously proposed a wide FOV head mounted projective display (HMPD) using a hyperboloidal semitransparent mirror and a semi-transparent retroreflective screen, called the wearable HHMPD [1]. Main features of the wearable HHMPD include a horizontal FOV of 110 degrees and a visual acuity of around 20/200. Using the wearable HHMPD, we then conducted a user study investigating the effects of a wide FOV in augmented reality (AR) [2]. Results show that target discovery rates consistently drop with in-view labelling and increase with in-situ labelling as display angle approaches 100 degrees of FOV. Past this point, the performances of the two view management methods begin to converge, suggesting equivalent discovery rates at approximately 130 degrees of FOV. Results also indicate that users exhibited lower discovery rates for targets appearing in peripheral vision, and that there is little impact of FOV on response time and mental workload.

A Robust Camera-Based Method for Optical Distortion Calibration of Head-Mounted Displays

One of the problems in using HMDs is that the virtual images shown through the HMDs are usually warped due to their optical distortions. In order to correctly compensate the optical distortions through a predistortion technique, accurate values of the distortion parameters are required. Although several distortion calibration methods have been developed in prior work, these methods have some limitations. In this paper, we propose a method for accurately estimating the optical distortion parameters of both immersive and (optical) see-through HMDs, without the limitations. The proposed method is based on photogrammetry and considers not only the radial distortion but also the tangential distortion. Its effectiveness, including the effects of different coefficient orders of radial and tangential distortions, are evaluated through an experiment conducted with two different HMDs, an optical see-through head-mounted projection display (HMPD) and a commercially available immersive HMD. According to the experimental results, the proposed method showed significantly lower reprojection and line-fitting errors than a previous method proposed by Owen , and the radial distortion coefficients estimated by the proposed method were significantly more accurate than the nominal values obtained from the HMD optics prescription. In addition, when both the radial and tangential distortions were considered, the proposed method was significantly more effective than when only the radial distortion was considered. We also discuss an OpenCV-based simple implementation of a distortion correction method.

投影式头戴静脉显像光学系统的设计

投影式头戴静脉显像光学系统的设计

Implementation and Evaluation of a Wide-view Head Mounted Projective Display with a Semi-transparent Retro-reflective Screen(<Special Issue>Mixed Reality)

Implementation and Evaluation of a Wide-view Head Mounted Projective Display with a Semi-transparent Retro-reflective Screen(<Special Issue>Mixed Reality)

Design of a polarized head-mounted projection display using ferroelectric liquid-crystal-on-silicon microdisplays

It has been a common problem in optical see-through head-mounted displays that the displayed image lacks brightness and contrast compared with the direct view of a real-world scene. This problem is aggravated in head-mounted projection displays in which multiple beam splitting and low retroreflectance of a typical retroreflective projection screen yield low luminous transfer efficiency. To address this problem, we recently proposed a polarized head-mounted projection display (p-HMPD) design where the polarization states of the light are deliberately manipulated to maximize the luminous transfer efficiency. We report the design of a compact p-HMPD prototype system using a pair of high-resolution ferroelectric liquid-crystal-on-silicon (FLCOS) microdisplays. In addition to higher resolution, the FLCOS displays have much higher optical efficiency than a transmissive-type liquid crystal display (LCD) and help to further improve the overall light efficiency and image quality. We detail the design of a compact illumination unit for the FLCOS microdisplay, also commonly referred to as the light engine, and a projection lens, both of which are key parts of the p-HMPD system. The performances of the light engine and projection lens are analyzed in detail. Finally, we present the design of a compact p-HMPD prototype using the custom-designed light engine and projection optics.

8.3: Design of a Compact Light Engine for FLCOS Microdisplays in a p‐HMPD System

AbstractWe have designed a compact light engine for a ferroelectric Liquid‐crystal‐on‐Silicon (FLCOS) microdisplay used in a polarized head mounted projection display (p‐HMPD). In the light engine, the polarization of the light is manipulated in order to achieve a compact structure and a mirror based tapered light pipe is designed to improve the light efficiency and image uniformity. The performance of the light engine is analyzed based on the simulation results using LightTools.

Characterizing polarization management in a p-HMPD system

It has been a common challenge to operate optical see-through head-mounted displays in well-lit environments due to the low image brightness and contrast compared with the direct view of a real-world scene. This problem is aggravated in the design of a see-through head-mounted projection display (HMPD) in which the projected light is split twice by a beam splitter and further attenuated greatly by a retroreflective screen. A polarizing head-mounted projection display (p-HMPD) design was recently proposed to enhance the overall flux transfer efficiency and thus increase the brightness and contrast of displayed images. Different from the conventional nonpolarizing HMPD designs, the light polarization states in the p-HMPD system are deliberately manipulated to maximize the flux transfer efficiency, which can potentially result in three times higher efficiency than that of a nonpolarizing HMPD. By measuring the Mueller matrices of the major elements in both a p-HMPD and a nonpolarizing HMPD, we characterize the polarization dependence of each element on incident angles and wavelengths, and also investigate the depolarization effect of the retroreflective screen. Based on these experimental results, we further examine the overall luminance efficiencies of the two types of systems and analyze how various aspects of display performances are affected by the angular and chromatic dependence of the polarization components.

Calibration of an HMPD-Based Augmented Reality System

In augmented reality (AR) applications, accurately registering a virtual object with its real counterpart is a challenging problem. The size, depth, and geometry, as well as the physical attributes of the virtual object, have to be rendered precisely relative to a physical reference. This paper presents a systematic calibration process to address the registration challenge in a custom-designed AR system, which is based upon recent head-mounted projective display (HMPD) technology. Following a concise review of the HMPD concept and our system configuration, we first present a computational model of the HMPD viewing system and requirements for the system calibration. Then, we describe, in detail, the calibration procedures to obtain estimates of unknown transformations, summarize the application of the estimates in a customized graphics rendering toolkit, and discuss the evaluation experiments and observations. Finally, the implementation of a testbed to demonstrate a successful registration is briefly described, and experimental results are presented

Design of a bright polarized head-mounted projection display

In optical see-through head-mounted displays, it has been a common challenge that the displayed image lacks brightness and contrast compared with the direct view of a real-world scene. Consequently, such displays are usually used in dimmed lighting conditions, which limits the feasibility of applying such information displays outdoors or in scenarios where well-lit environments, such as in operation rooms, are required. The lack of image brightness is aggravated in the design of a see-through head-mounted projection display (HMPD). For instance, the overall flux transfer efficiency of existing HMPD designs is less than 10%. The design of a polarized head-mounted projection display (p-HMPD) is presented. The images of a p-HMPD system can potentially be three times brighter than those in existing HMPD designs. It is further demonstrated that the p-HMPD design is able to dramatically improve image brightness, contrast, and color vividness with experimental results. Finally, the design of a compact optical system and helmet prototype is described.

Development of Head-Mounted Projection Displays for Distributed, Collaborative, Augmented Reality Applications

Distributed systems technologies supporting 3D visualization and social collaboration will be increasing in frequency and type over time. An emerging type of head-mounted display referred to as the head-mounted projection display (HMPD) was recently developed that only requires ultralight optics (i.e., less than 8 g per eye) that enables immersive multiuser, mobile augmented reality 3D visualization, as well as remote 3D collaborations. In this paper a review of the development of lightweight HMPD technology is provided, together with insight into what makes this technology timely and so unique. Two novel emerging HMPD-based technologies are then described: a teleportal HMPD (T-HMPD) enabling face-to-face communication and visualization of shared 3D virtual objects, and a mobile HMPD (M-HMPD) designed for outdoor wearable visualization and communication. Finally, the use of HMPD in medical visualization and training, as well as in infospaces, two applications developed in the ODA and MIND labs respectively, are discussed.

System and Interface Framework for SCAPE as a Collaborative Infrastructure

We have developed a multi-user collaborative infrastructure, SCAPE (an acronym for Stereoscopic Collaboration in Augmented and Projective Environments), which is based on recent advancement in head-mounted projective display (HMPD) technology. SCAPE combines the functionalities of an interactive workbench and a room-sized immersive display to concurrently create both exocentric and egocentric perspectives. SCAPE intuitively provides a shared space in which multiple users can simultaneously interact with a 3D synthetic environment from their individual viewpoints, and each user has concurrent access to the environment from multiple perspectives at multiple scales. SCAPE also creates a platform to merge the traditionally separate paradigms of virtual and augmented realities. In this paper, we discuss the design principles we have followed to conceptualize the SCAPE system and briefly summarize SCAPE's hardware implementation. Furthermore, we discuss in detail the high-level design and implementation of the SCAPE architecture, and present a set of unique widget interfaces currently available in our implementation that enable and facilitate interaction and cooperation. Finally, we demonstrate SCAPE's unique visualization and interface capabilities via a testbed application— Aztec Explorer.

Design of an ultralight and compact projection lens.

Driven by the need for lightweight head-mounted displays, we present the design of an ultralight and compact projection lens for a head-mounted projective display (HMPD). An HMPD consists of a pair of miniature projection lenses, beam splitters, and miniature displays mounted on the helmet and retroreflective sheeting materials placed strategically in the environment. The HMPD has been proposed recently as an alternative modality for three-dimensional visualization. After demonstrating the concept, building a first-generation custom-designed prototype, and investigating perception issues and application potentials, we designed an ultralight and compact projective lens with a diffractive optical element (DOE), plastic components, and aspheric surfaces for the next-generation prototype. The key contribution here lies in the conception, optimization, and assessment of the projection optics. Thus a brief review of the HMPD technology and related research is followed by a detail discussion of the conception and optimization of the ultralight and high-performance projection optics. The design of the DOE will be particularly described in detail. Finally, the diffraction efficiency of the DOE will be evaluated, and the overall performance of the optics will be assessed in both object space for the optical designer and visual space for possible end-users of the technology.