Space-bandwidth product in digital holography is defined as a product of spatial dimension and bandwidth of the sampled space. This limitation results in a narrow field of view or a small eye-box in holographic near-eye display. Utilizing additional micro-structured or non-periodic optics is a well-known approach that bypasses this physical constraint. However, these approaches require precise alignment and suffer from low signal-to-noise ratio in the reconstructed holographic image. In this work, we propose a novel prototype of holographic near-eye display with wide field of view achieved by axially overlapped holographic projection. The feasibility of the proposed work is evaluated with simulation and experimental results
Speckles, resultant to the randomized interference of coherent fields, are inherent in holographic displays. Speckle in holographic displays leads to low signal-to-ratio in the reconstructed holographic images and causes potential eye-safety issues. In this invited paper, recent works on speckle reduction in holographic displays either by modulating the light source module or by temporally multiplexing the computer generated holograms will be introduced.
We first discuss the key factors of augmented reality (AR) and virtual reality (VR) displays. Various requirements for immersive experiences are categorized as six factors that must be considered when designing the AR/VR head-mounted displays (HMDs). These factors have a strong correlation with other factors and should maintain a moderate balance between them. Based on recent researches we second introduce various technologies for AR/VR. By comparing the pros and cons of each method, we discuss the progression of AR/VR devices that can provide more affordable HMD devices for the public.
Even now that DNA test has become common, latent fingerprints are still a useful evidence for finding criminals. However, the latent fingerprints are often damaged and overlapped with each other. At present, these overlapped fingerprints are separated manually by a person. It is not only time-consuming task, but also less likely to be adopted as evidence because it is difficult to rule out of the intention of a person. In this paper, non-destructive method to capture and separate overlapped fingerprints using digital holography and machine learning is presented and demonstrated.
This paper proposes a method for implementing off-axis reflective digital holography using a single diffraction grating element. The typical off-axis digital holography uses a beam splitter to form interference beams, and obtain off-axis interference patterns by tilting a mirror. We use a diffraction grating to replace the mirror and beam splitter with one element. The grating element separates the incident beam into +1 and -1 orders, and the separated beams are used as the reference beam and the signal beam, respectively. The signal beam reflects off the tilted specimen and returns to the grating element. The diffraction grating acts as a beam combiner to diffract the tilted signal beam again to interfere the signal beam with the reference beam. Therefore, the diffraction grating device acts as a multi-functional device that simultaneously performs the functions of the beam splitter and mirror. We set the image sensor plane at an angle perpendicular to the tilted signal beam. As a result, the reference beam can be incident on the image sensor plane in the form of off-axis. Since the two devices required in the conventional off-axis digital holography can be implemented as a single grating component, a cost effective and compact system can be realized.
Digital holography is widely known as one of the techniques reconstructing a depth profile of the object. For digital holography (DH), the light source that has a long coherence length such as laser or laser diode is generally recommended. Recently, digital holographic microscopy (DHM) utilizing light emitting diode (LED) as a light source has attracted attention. However, it has to satisfy certain conditions for LED be utilized in off-axis DHM as it has small coherence length. Due to this fact, the hologram cannot be captured from the other side of a beam splitter. Therefore, we propose an LED-based off-axis reflective DHM that combines a 4-f system that optically relays the field to the sensor plane of charge-coupled device (CCD). We analyze the reason why the sample plane has to be relayed by 4-f system. We provide experimental results to verify the necessity of relay optics in LED-based reflective off-axis DHM.
In this paper, we propose the index matched anisotropic crystal lens. The proposed optical element acts as a transparent glass in extraordinary polarized light and a lens in ordinary polarized light. The conceptual diagram and principle of the index matched anisotropic crystal lens are presented and the ray tracing simulation is performed to verify and analyze the functionality and the distortion of the real world scene. The index matched anisotropic crystal lens is implemented with calcite and the index matching liquid. The preliminary system to show the feasibility of the proposed optical element is implemented. The lens mode and the transparent mode are presented and the distortion along the incident direction of the light is also analyzed by the experiment. It is expected that the index matched anisotropic crystal lens can be a good candidate for the head-up display and head-mounted display.
A head-mounted compressive three-dimensional (3D) display system is proposed by combining polarization beam splitter (PBS), fast switching polarization rotator and micro display with high pixel density. According to the polarization state of the image controlled by polarization rotator, optical path of image in the PBS can be divided into transmitted and reflected components. Since optical paths of each image are spatially separated, it is possible to independently focus both images at different depth positions. Transmitted p-polarized and reflected s-polarized images can be focused by convex lens and mirror, respectively. When the focal lengths of the convex lens and mirror are properly determined, two image planes can be located in intended positions. The geometrical relationship is easily modulated by replacement of the components. The fast switching of polarization realizes the real-time operation of multi-focal image planes with a single display panel. Since it is possible to conserve the device characteristic of single panel, the high image quality, reliability and uniformity can be retained. For generating 3D images, layer images for compressive light field display between two image planes are calculated. Since the display panel with high pixel density is adopted, high quality 3D images are reconstructed. In addition, image degradation by diffraction between physically stacked display panels can be mitigated. Simple optical configuration of the proposed system is implemented and the feasibility of the proposed method is verified through experiments.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.