ARTICLE | doi:10.20944/preprints202211.0281.v1
Subject: Physical Sciences, Optics Keywords: diffractive lens; imaging; Lucy-Richardson-Rosen algorithm; holography; incoherent imaging; telescope; photolithography; computational imaging
Online: 15 November 2022 (07:52:16 CET)
Direct imaging systems that create an image of an object directly on the sensor in a single step are prone to many constraints as a perfect image is required to be recorded within this step. In designing high resolution direct imaging systems with a diffractive lens, the outermost zone width either reaches the lithography limit or the diffraction limit itself imposing challenges in fabrication. However, if the imaging mode is switched to an indirect one consisting of multiple steps to complete imaging, then different possibilities open up. One such methods is the widely used indirect imaging method with Golay configuration telescopes. In this study, a Golay-like configuration has been adapted to realize a large area diffractive lens with three sub-aperture diffractive lenses. The sub-aperture diffractive lenses are not required to collect light and focus them to a single point as in a direct imaging system but to focus independently on different points within the sensor area. This approach of Large Area Diffractive lens with Integrated Sub-Apertures (LADISA) relaxes the fabrication constraints and allows the sub-aperture diffractive elements to have a larger outermost zone width and smaller area. The diffractive sub-apertures were manufactured using photolithography. The fabricated diffractive element has been implemented in indirect imaging mode using non-linear reconstruction and Lucy-Richardson-Rosen algorithm with synthesized point spread functions. The computational optical experiments revealed an improved optical and computational imaging resolutions compared to previous studies.
ARTICLE | doi:10.20944/preprints201807.0410.v1
Subject: Physical Sciences, Applied Physics Keywords: solar windows; advanced glazings; diffractive elements; light trapping; photovoltaics
Online: 23 July 2018 (10:18:54 CEST)
We report on the study of energy-harvesting performance in medium-size (400 cm2) glass-based semitransparent solar concentrators employing edge-mounted photovoltaic modules. Systems using several different types of glazing system architecture and containing embedded diffractive structures are prepared and characterized. The technological approaches to the rapid manufacture of large-area diffractive elements suitable for use in solar window-type concentrators are described. These elements enable the internal deflection and partial trapping of light inside glass-based concentrator windows. We focus on uncovering the potential of pattern-transfer polymer-based soft lithography for enabling both the improved photon collection probability at solar cell surfaces, and the up-scaling of semitransparent solar window dimensions. Results of photovoltaic characterization of several solar concentrators employing different internal glazing-system structure and diffractive elements produced using different technologies are reported and discussed.
REVIEW | doi:10.20944/preprints202012.0009.v1
Subject: Physical Sciences, Acoustics Keywords: Holography; diffractive optics; incoherent optics; Fresnel incoherent correlation holography; Imaging; speckle
Online: 1 December 2020 (09:55:45 CET)
Fresnel incoherent correlation holography (FINCH) is a well-established incoherent imaging technique. In FINCH, three self-interference holograms are recorded with calculated phase differences between the two interfering, differently modulated object waves and projected into a complex hologram. The object is reconstructed without the twin image and bias terms by a numerical Fresnel back propagation of the complex hologram. A modified approach to implement FINCH by a single camera shot by pre-calibrating the system involving recording of the point spread function library and reconstruction by a non-linear cross-correlation has been introduced recently. The expression of the imaging characteristics from the modulation functions in original FINCH and the modified approach by pre-calibration in spatial and polarization multiplexing schemes are reviewed. The study reveals that a reconstructing function completely independent of the function of the phase mask is required for the faithful expression of the characteristics of the modulating function in the image reconstruction. In polarization multiplexing method by cross-correlation, a partial expression was observed, while in spatial multiplexing method by cross-correlation, the imaging characteristics converged towards a uniform behavior.
ARTICLE | doi:10.20944/preprints202004.0423.v1
Subject: Medicine & Pharmacology, Ophthalmology Keywords: mix-and-match; extended-depth-of-focus intraocular lens; diffractive multifocal intraocular lens; stereopsis
Online: 24 April 2020 (03:30:03 CEST)
Purpose: To evaluate clinical outcomes after bilateral mix-and-match cataract surgery using extended depth of focus (EDOF) and diffractive multifocal (DMF) intraocular lenses (IOLs). Methods: Thirty-seven patients received Tecnis Symfony EDOF IOL (ZXR00) implantation in the dominant eye, and Tecnis +3.25 DMF IOL (ZLB00) in the non-dominant eye. Patients were followed for 3 months, and uncorrected and corrected distance visual acuity (UDVA, CDVA) , uncorrected intermediate and near visual acuity (UIVA, UNVA), contrast sensitivity, defocus curves, stereopsis, and patient satisfaction were assessed. Results: At 3 months, mean logMAR UDVA was 0.07 ± 0.09 in EDOF IOL eyes, 0.12 ± 0.11 in DMF IOL eyes, and 0.02 ± 0.05 in both eyes. UIVA was 0.11 ± 0.11 in EDOF IOL eyes, 0.16 ± 0.12 in DMF IOL eyes, and 0.04 ± 0.07 in both eyes. UNVA was 0.25 ± 0.15 in EDOF IOL eyes, 0.22 ± 0.16 in DMF IOL eyes, and 0.13 ± 0.13 in both eyes. Thirty patients(81.1%) were more than satisfied with near vision, and 8 patients(21.6%) complained of severe glare and halo. Spectacle independence for near vision was achieved in 34 patients(91.9%), and 31 patients(83.8%) had better than a 50 second arc of stereopsis. Conclusion: Mix-and-match cataract surgery with EDOF and DMF IOL implantation provided good visual outcomes through all distances. Also excellent patient satisfaction was achieved with high level of spectacle independence and minimal photic phenomena.
REVIEW | doi:10.20944/preprints202205.0399.v1
Subject: Physical Sciences, Optics Keywords: Holography; computational imaging; non-linear reconstruction; Fresnel incoherent correlation holography; coded aperture imaging; rotating point spread function; diffractive optics; scattering.
Online: 30 May 2022 (11:37:04 CEST)
Indirect imaging methods involve at least two steps, namely optical recording, and computational reconstruction. The optical recording process uses an optical modulator that transforms the light from the object into a typical intensity distribution. This distribution is numerically processed to reconstruct the object’s image corresponding to different spatial and spectral dimensions. There have been numerous optical modulation functions and reconstruction methods developed in the past years for different applications. In most cases, a compatible pair of optical modulation function and reconstruction method gives optimal performance. A new reconstruction method termed non-linear reconstruction (NLR) was developed in 2017 to reconstruct the object image in the case of optical scattering modulators. During the years, it was revealed that the NLR could reconstruct an object’s image modulated by an axicons, bifocal lenses and even exotic spiral diffractive elements, which generate deterministic optical fields. Apparently, NLR seems to be a universal reconstruction method for indirect imaging. In this review, the performance of NLR has been investigated for many deterministic and stochastic optical fields. Simulation and experimental results for different cases are presented and discussed.