ABSTRACT
The Optica Topical Meeting on Digital Holography and 3D Imaging (DH) was held 14-17 August 2023 in Boston, Massachusetts. The meeting was organized co-jointly with the Optica Imaging Congress. Feature issues based on the DH meeting series have been released by Applied Optics (AO) since 2007. Since 2017, AO and the Journal of the Optical Society of America A (JOSA A) have presented a feature issue in each journal. This feature issues includes 17 papers in AO and 9 in JOSA A. Together they cover a large range of topics, reflecting the rapidly expanding techniques and applications of digital holography and 3D imaging. The upcoming DH Conference (DH 2024) will be held from 3 to 6 June in Paestum, Italy.
ABSTRACT
The Optica Topical Meeting on Digital Holography and 3D Imaging (DH) was held 14-17 August 2023 in Boston, Massachusetts. The meeting was organized co-jointly with the Optica Imaging Congress. Feature issues based on the DH meeting series have been released by Applied Optics (AO) since 2007. Since 2017, AO and the Journal of the Optical Society of America A (JOSA A) have presented a feature issue in each journal. This feature issues includes 17 papers in AO and 9 in JOSA A. Together they cover a large range of topics, reflecting the rapidly expanding techniques and applications of digital holography and 3D imaging. The upcoming DH Conference (DH 2024) will be held from 3 to 6 June in Paestum, Italy.
ABSTRACT
The high angular and spectral selectivity of volume holograms have been used in fields like astronomy, spectroscopy, microscopy, and optical communications to perform spatial filtering and wavefront selection. In particular, imaging systems that utilize volume holograms to perform range-based wavefront selection have allowed for the potential to have full 24-hour observational custody of artificial satellites by enabling daytime observations. We previously introduced the Advanced Volume Holographic Filter (AVHF) which demonstrated a significant system bandwidth improvement while maintaining high angular selectivity. Presented here is a theoretical basis for maximizing the bandwidth of the AVHF systems. We experimentally demonstrate an improvement of 40.7-41.4x compared to the un-optimized AVHF systems.
ABSTRACT
We are presenting the optical ray tracing as well as an experimental prototype of a curved waveguide combiner with pupil expansion for augmented reality (AR) and mixed reality (MR) glasses. The curved waveguide combiner takes advantage of holographic optical elements both for injection and extraction of the image to correct the aberrations introduced during the propagation of light inside the waveguide. The holographic curved combiner presented has a cylindrical outer radius of curvature of 171.45 mm with a field of view of 13° (H) × 16° (V) at a viewing distance of 1 cm with a 5 × horizontal 1 dimension pupil expansion for an eyebox of 6.2 mm × 42.7 mm.
ABSTRACT
Thick volume Bragg gratings (VBG) have been used for wavefront selectivity in various applications such as data storage, endoscopy, or astronomic observation. However, a single thick grating is also selective in wavelength, severely limiting the spectral throughput of the system. Recently, our group introduced a two element Advanced Volume Holographic Filter (AVHF) where the first, dispersive Bragg grating is coupled to a thick VBG such that it dramatically improves the spectral bandwidth, and ultimately enhances the signal to noise ratio of polychromatic sources. Still, the two grating AVHF configuration introduced wavelength dispersion which prevents usage of the filter in imaging systems. Here, we present a solution to this problem by introducing a third diffraction grating that compensates for the dispersion of the two initial gratings. Using both simulation and experimental implementation of a visible-based, broadband AVHF system, the spectral dispersion was improved by a factor of up to 41 × compared to our previous system, re-collimating the output filtered beam. This new AVHF system can be utilized in imaging applications with noisy environments requiring filtration of a polychromatic source.
ABSTRACT
We present the performance analysis and specifications of a portable auto-phoropter system that can be employed for fast refractive assessment of a large population. A customized Shack-Hartmann wavefront sensor is developed to accurately measure the defocus and astigmatism of the eye within ±10D and ±6D, respectively. Three fluidic lenses are designed to correct the vision in real time. A digital Snellen chart is integrated into the system to validate the accuracy of the measurement and the correction by means of achieving 20/20 vision. The refractive error of eight subjects (16 eyes) has been measured objectively (without patient's feedback) using the proposed system and the results are compared with their clinical prescription through the Bland-Altman method. It is shown that the auto-phoropter takes less than 8 s to measure and correct the eye refractive error with an accuracy of ±0.25D.
Subject(s)
Astigmatism , Lens, Crystalline , Lenses , Refractive Errors , Astigmatism/diagnosis , Humans , Refractive Errors/diagnosis , Visual AcuityABSTRACT
We present a new type of filter that improves the SNR of systems where polychromatic signal and noise are located at different distances within the same line of sight. The filter is based on holographic technology that allows for the discrimination of wavefronts by range. In using a combination of two holographic elements, a pre-disperser and a thick volume hologram, we were able to significantly increase the spectral bandwidth of the filter, from 9nm without the pre-disperser to 70nm with both holographic elements. Laboratory proof of concept demonstrated that such a filter is capable of an SNR improvement of 15 dB for a monochromatic source, and up to 7.6 dB for a polychromatic source. This filter can find applications in astronomic observation, satellite or space debris tracking, and free-space optical communication.
ABSTRACT
This feature issue of JOSA A and Applied Optics is dedicated to the fourteenth OSA Topical Meeting "Digital Holography and 3D Imaging" held 22-26 June 2020 in a virtual meeting. The conference, taking place every year, is a focal point for global technical interchange in the field of digital holography and 3D imaging, providing premier opportunities for people working in the field to present their new advances in research and development. Papers presented at the meeting highlight current research in digital holography and three-dimensional imaging, including interferometry, phase microscopy, phase retrieval, novel holographic processes, 3D and novel holographic displays, integral imaging, computer-generated holograms, compressive holography, 3D holographic display, AR display, full-field tomography, specific image and signal processing, and holography with various light sources, including coherent to incoherent and x-ray to terahertz waves. Techniques of digital holography and of 3D imaging have numerous applications, such as the state-of-the-art technological developments that are currently underway and stimulate further novel applications of digital holography and 3D imaging in biomedicine, deep learning, and scientific and industrial metrologies.
ABSTRACT
Pupil expansion using waveguide propagation and pupil replication has been a popular method of developing head-up displays and near-to-eye displays. This paper examines one of the limits of pupil replication, which involves projecting images at a finite distance through a single waveguide by holographic optical elements and seeing the image doubling artifact. A Zemax model and a demonstrator were developed to determine the cause of image doubling. A relationship between the designed outcoupled image distance of a waveguide, pupil size, optical path length, and angle of image doubling is established. In waveguide pupil replication, the internally propagating light should be close to collimated to mitigate image doubling. We also provide a solution to project the image at different distances, which is an important factor for some applications, such as automotive head-up display and the seamless integration of augmented reality information with the natural environment.
ABSTRACT
This feature issue of JOSA A and Applied Optics is dedicated to the fourteenth OSA Topical Meeting "Digital Holography and 3D Imaging" held 22-26 June 2020 in a virtual meeting. The conference, taking place every year, is a focal point for global technical interchange in the field of digital holography and 3D imaging, providing premier opportunities for people working in the field to present their new advances in research and development. Papers presented at the meeting highlight current research in digital holography and three-dimensional imaging, including interferometry, phase microscopy, phase retrieval, novel holographic processes, 3D and novel holographic displays, integral imaging, computer-generated holograms, compressive holography, 3D holographic display, AR display, full-field tomography, specific image and signal processing, and holography with various light sources, including coherent to incoherent and x-ray to terahertz waves. Techniques of digital holography and of 3D imaging have numerous applications, such as the state-of-the-art technological developments that are currently underway and have also stimulated further novel applications of digital holography and 3D imaging in biomedicine, deep learning, and scientific and industrial metrologies.
ABSTRACT
Tunable spherical fluidic lenses are among the most essential components in adaptive optics. However, fabricating cylindrical tunable lenses has proven more challenging, mainly due to the difficulty in eliminating the defocus component. We demonstrate a parametric approach to minimize the defocus in cylindrical tunable fluidic lenses. We theoretically model and experimentally verify that a dog-bone-shaped tunable cylindrical fluidic lens exhibits almost pure cylindrical performance within the range of ${\pm{\rm 5D}}$ of astigmatism. We anticipate these results will facilitate the use of tunable cylindrical fluidic lenses in adaptive optics applications and particularly ophthalmic devices, where rapid and reliable wavefront correction is required.
ABSTRACT
The OSA Topical Meeting on Digital Holography and 3D Imaging (DH) was held 20-23 May 2019 in Bordeaux, France. Feature issues based on the DH meeting series have been released by Applied Optics (AO) since 2007. This year, AO and the Journal of the Optical Society of America A (JOSA A) jointly decided to have one such feature issue in each journal. This feature issue includes 46 papers in AO and 9 in JOSA A and covers a large range of topics, reflecting the rapidly expanding techniques and applications of digital holography and 3D imaging. The upcoming DH Conference (DH 2020) will be held from 22 to 26 June in Vancouver, Canada, as part of the OSA Imaging and Applied Optics Congress.
ABSTRACT
Beam steering in lidar applications presents an important engineering problem, as researchers seek to achieve the highest possible field of view with low energy cost and rapid refresh rate. Non-mechanical beam-steering technologies that exist today are known to achieve a low energy cost and rapid refresh rate, but they have a narrow angular range. A method by which the diffraction angle from a beam-steering device may be increased to cover a 4π sr solid angle is presented. Multiple holograms are recorded in the same volume hologram in a process called multiplexing. This multiplexed hologram can diffract light over a solid angle of 2π sr. To increase the angular coverage up to 4π sr, a hemispheric lens is attached to the volume hologram. Secondary holographic optical elements coated on the lens surface further diffract the light, directing it to a theoretical maximum of 4π sr. An early prototype demonstrates five distinct diffraction angles, ranging from 20° to 150°, which covers a solid angle around 90% of the entire sphere while maintaining beam collimation.
ABSTRACT
A method of head-up display is presented that uses an in-line surface relief grating attached to a waveguide propagation head-up display to achieve a large field of view without the need for large-projection optics. Horizontal pupil expansion is achieved using an extraction hologram that is multiple times the size of the injection hologram and is recorded with modulated diffraction efficiency. Vertical pupil expansion is achieved by coupling the surface relief grating to the waveguide surface between the injection and extraction holograms. The grating replicates the beam along the propagation direction, which allows for a larger field of view at the extraction. Using this technique, both a Zemax OpticStudio computer model and a physical system demonstrator achieve a field of view of 16∘×14.25∘.
ABSTRACT
The OSA Topical Meeting on Digital Holography and 3D Imaging (DH) was held 20-23 May 2019 in Bordeaux, France. Feature issues based on the DH meeting series have been released by Applied Optics (AO) since 2007. This year, AO and the Journal of the Optical Society of America A (JOSA A) jointly decided to have one such feature issue in each journal. This feature issue includes 46 papers in AO and 9 in JOSA A and covers a large range of topics, reflecting the rapidly expanding techniques and applications of digital holography and 3D imaging. The upcoming DH Conference (DH 2020) will be held from 22 to 26 June in Vancouver, Canada, as part of the OSA Imaging and Applied Optics Congress.
ABSTRACT
Head-up displays (HUDs) are used in aircraft to overlay relevant flight information on the vehicle's externals for pilots to view with continued focus on the far field. In these systems, the field of view (FOV) is traditionally limited by the size of the projection optics. Though classical HUD systems take a significant amount of space in the flight deck, they have become a necessity in avionic transportation. Our research aims to reduce the size of the HUD footprint while offering a wide FOV projected in the far field with an expanded pupil. This has been accomplished by coupling the image-bearing light into a waveguide under total internal reflection conditions, redirecting that light in the orthogonal direction, and then outcoupling the light toward the pilot. Each step was achieved using holographic optical elements. The injection hologram has optical power to obtain longitudinal magnification, whereas the redirection hologram expands the pupil in one dimension and the extraction hologram expands the pupil in a second dimension. Varying diffraction efficiency along the direction of the light propagation ensures even image intensity throughout the expanded pupil. We used ray tracing optical simulations to optimize the design of the system and present a fully operational demonstrator of the HUD. This HUD produces an image with a FOV of 24°×12.6° at a viewing distance of 4.5 in. (114 mm) from the waveguide, with infinite longitudinal magnification and 1.9× by 1.6× horizontal and vertical pupil expansion, respectively.
ABSTRACT
Hybrid thermal-PV solar trough collectors combine concentrated photovoltaics and concentrated solar power technology to harvest and store solar energy. In this work, the optical and mechanical requirements for optimal efficiency are analyzed using non-sequential ray tracing techniques. The results are used to generate opto-mechanical tolerances that can be compared to those of traditional solar collectors. We also explore ideas on how to relieve tracking tolerances for single-axis solar collectors. The objective is to establish a basis for tolerances required for the fabrication and manufacturing of hybrid solar trough collectors.
ABSTRACT
The field of view of traditional heads-up display systems is limited by the size of the projection optics. Our research is focused on overcoming this limitation by coupling image-bearing light into a waveguide using holographic elements, propagating the light through that waveguide, and extracting the light several times with additional holographic optical elements. With this configuration, we demonstrated both longitudinal magnification and pupil expansion of the heads-up display. We created a ray-trace model of the optical system to optimize the component parameters and implemented the solution in a prototype that demonstrates the merit of our approach. Longitudinal magnification is achieved by encoding optical power into the hologram injecting the light into the waveguide, while pupil expansion is obtained by expanding the size of the hologram extracting the light from the waveguide element. To ensure uniform intensity of the image, the diffraction efficiency of the extracting hologram is modulated according to the position. Our design has a 12°×8° field of view at a viewing distance of 10 in. (250 mm), with infinite longitudinal magnification and a 1.7× lateral pupil expansion.
ABSTRACT
CLINICAL RELEVANCE: Currently eye examinations are usually based on autorefraction followed by subjective refraction (SR) with a phoropter. An automated phoropter that can also perform autorefraction may facilitate the optometric workflow. BACKGROUND: The efficiency and feasibility of an objective autorefraction and correction system are assessed by comparing objective refractive measurements with SR on the same subjects and evaluating the visual acuity (VA) values obtained after the objective refractive measurement and correction. METHODS: Objective autorefraction and correction was performed on 41 subjects using an automated binocular phoropter system. The auto-phoropter performs autorefraction by wavefront measurement and corrects the spherical and cylindrical errors with tunable fluidic lenses while the patient looks at a visual display inside the instrument. The instrument outputs are optometric constants of spherical and cylindrical aberrations. After measurement and automated correction of the refractive errors, the VA values were assessed by having the subjects look at an integrated Snellen chart. The objective measurement results were statistically compared with their SR. RESULTS: The correlations between SR and objective autorefraction and correction spherical equivalents (M) were 0.98 (0.97-0.99) and 0.96 (0.93-0.98), the vertical Jackson cross cylinder (J0) were 0.96 (0.92-0.98) and 0.95 (0.91-0.97), and the oblique Jackson cross cylinder (J45) were 0.73 (0.55-0.85) and 0.82 (0.69-0.90), for the right and left eyes, respectively, with the 95% confidence interval (CI) values in parentheses. 89.0% of the 82 eyes had at least 6/7.5 VA. CONCLUSIONS: A significant agreement between the SR and objective autorefraction and correction was observed. An all-objective refractive assessment with instantaneous verification may improve the precision of eye prescriptions and possibly reduce the procedure time.
ABSTRACT
Holographic three-dimensional (3D) display can be made very large using a modular system that allows seamless spatial tiling of multiple coarse integral holographic images.