Plasmonic color filter array based visible light spectroscopy

Compared with traditional Fabry–Perot optical filters, plasmonic color filters could greatly remedy the complexity and reduce the cost of manufacturing. In this paper we present end-to-end demonstration of visible light spectroscopy based on highly selective plasmonic color filter array based on resonant grating structure. The spectra of 6 assorted samples were measured using an array of 20 narrowband color filters and detected signals were used to reconstruct original spectra by using new unmixing algorithm and by solving least squares problem with smoothing regularization. The original spectra were reconstructed with less than 0.137 root mean squared error. This works shows promise towards fully integrating plasmonic color filter array in imagers used in hyperspectral cameras.

Fluorescence Enhanced Optical Resonator Constituted of Quantum Dots and Thin Film Resonant Cavity for High-Efficiency Reflective Color Filter

Conventional color filters selectively absorb a part of the backlight while reflecting or transmitting other light, resulting in the problem of low efficiency and energy wasting. For this problem, a new concept of fluorescence enhanced optical resonator was proposed and verified in this paper. The new structure consists of structural color filter and light-conversion material. Specially, a thin film resonant cavity was designed, and InP/ZnSe/ZnS quantum dots were inserted inside the resonator. When illuminated by sunlight, the novel fluorescence enhanced optical resonator could not only reflect the specific light, but also convert absorbed energy into desired light, leading to the utilization efficiency improvement of solar energy. An all-dielectric red fluorescence enhanced optical resonator was fabricated, with peak equivalent reflectance up to 105%. Compared with a thin film resonator, the enhancement coefficient of the as-proposed structure is about 124%. The new optical structure can utilize solar source efficiently, showing application potential as the next generation of reflective color filters for display.

Detecting Binocular Diplopia in Orbital Floor Blowout Fractures: Superiority of the Orthoptic Approach

Background and Objectives: In patients with orbital floor blowout fracture (OFBF), accurate diagnosis of ocular motility disorder is important for decisions about conservative or surgical therapy. However, the accuracy of the traditional test for detecting binocular diplopia/ocular motility disorder using a moving pencil or finger (hereinafter, “finger test”) has been generally accepted as correct and has not been subject to scrutiny so far. Hence, its accuracy relative to full orthoptic examination is unknown. Materials and Methods: In this paper, the results of the “finger test” were compared with those derived from a complex examination by orthoptic tests (considered “true” value in patients with OFBF). Results: “Finger test” detected ocular motility disorder in 23% of patients while the full orthoptic examination proved much more efficient, detecting ocular motility disorder in 65% of patients. Lancaster screen test and test with color filters were the most important tests in the battery of the orthoptic tests, capable of identifying 97.7% and 95.3% of patients with ocular motility disorder, respectively. Still, none of the tests were able to correctly detect all patients with ocular motility disorder in itself. Conclusions: As the presence of ocular motility disorder/binocular diplopia is an important indication criterion for the surgical solution of the orbital floor blowout fracture, we conclude that a complex orthoptic evaluation should be always performed in these patients.

Structural Compression of Convolutional Neural Networks with Applications in Interpretability

Deep convolutional neural networks (CNNs) have been successful in many tasks in machine vision, however, millions of weights in the form of thousands of convolutional filters in CNNs make them difficult for human interpretation or understanding in science. In this article, we introduce a greedy structural compression scheme to obtain smaller and more interpretable CNNs, while achieving close to original accuracy. The compression is based on pruning filters with the least contribution to the classification accuracy or the lowest Classification Accuracy Reduction (CAR) importance index. We demonstrate the interpretability of CAR-compressed CNNs by showing that our algorithm prunes filters with visually redundant functionalities such as color filters. These compressed networks are easier to interpret because they retain the filter diversity of uncompressed networks with an order of magnitude fewer filters. Finally, a variant of CAR is introduced to quantify the importance of each image category to each CNN filter. Specifically, the most and the least important class labels are shown to be meaningful interpretations of each filter.

Hayabusa2 Returned Samples: First Results From the MicrOmega Investigation Within the ISAS Curation Facility

<p><strong>Introduction:</strong> On December 6, 2020, the Hayabusa2 mission successfully returned to Earth ~ 5.4 g of samples collected at the surface of the C-type asteroid Ruygu [1,2]. Its surface was first sampled on February 22, 2019, then on July 12, 2019, close to a 10-meter large artificial crater, so as to possibly access sub-surface material [3]. The collected samples are now kept at the Extraterrestrial Samples Curation Center of JAXA at ISAS in Sagamihara, Japan, for a first round of preliminary analyses, with the objective to characterize in a non-destructive manner both the bulk samples and a few hundreds of grains extracted from them [4]. In particular, the objective is 1) to support their further detailed characterization by the international initial analysis teams, which will start their activity in July 2021, and 2) to catalog the grains, accessible to the international community through AO selection, starting mid-2022.</p> <p>The preliminary characterization of these samples is being conducted with a visible microscope with four color filters, a FTIR spectrometer operating in the 1-5 µm range and MicrOmega, a hyperspectral NIR microscope developed at Institut d'Astrophysique Spatiale (Université Paris-Saclay/CNRS, Orsay, France), operating in the near-infrared range (0.99-3.65 µm) [5]. It is noteworthy that never before have the preliminary analyses of returned extraterrestrial samples included the characterization by a NIR hyperspectral microscope.</p> <p><strong>Results: </strong>Preliminary outcomes of the analyses performed with MicrOmega will be presented at the conference. In particular, the question of the representativity of the samples collected by the Hayabusa2 spacecraft will be addressed thanks to the comparison of the spectra obtained by MicrOmega and the NIRS3 remote sensing IR spectrometer [6] which performed a spectral characterization (1.8-3.2 µm) of Ryugu's surface, including the sites of the samples' collection [7,8]. A preliminary analysis of the spatial compositional heterogeneity will be presented. Specific signatures, detected in grains typically present in <1% of the pixels, but of high relevance regarding the processes determining Ryugu formation and evolution, will also be discussed.</p> <p><strong>References: </strong>[1] Binzel R. P. et al. (2002), Physical Properties of Near-Earth Objects. pp. 255-271, [2] Vilas F. (2008) <em>The Astronomical Journal</em> 135 (4), 1101-1105, [3] Morota et al. (2020) <em>Science</em> 368, Issue 6491, pp. 654-659, [4] Yada T. et al., in preparation, [5] Bibring J.-P. et al. (2017) <em>Astrobiology</em> 17, Issue 6-7, pp.621-626, [6] Iwata T. et al. (2017) <em>Space Science Reviews</em> 208 (1-4), 317-337, [7] Kitazato K. et al. (2019) <em>Science</em> 364 (6437), 272-275, [8] Kitazato K. et al. (2020) <em>Nature Astronomy</em>, Volume 5, p. 246-250.</p>

Illumination Effect on Electrical Characteristics of Poly(3-hexylthiophene): TIPS-Pentacene Blend Thin-Film Transistor

Organic phototransistors capable of absorbing in the visible light spectrum without color filters are the best alternatives to conventional inorganic phototransistors. In this study, the effect of illumination on the electrical characteristics of a solution-processed poly(3-hexylthiophene): 6,13-bis(triisopropylsilylethynyl) pentacene-blend thin-film transistor (TFT) was investigated. The wavelengths of the irradiated light were determined from the absorbance spectrum of the blended film and changes in the transistor’s electrical characteristics were explained in relation to the electrical and light absorption properties of each component material. The photosensitivity and absorbing properties of the blended TFT were enhanced at 515 and 450 nm and exhibited positively shifted threshold voltages under incident light. The results indicated that the photo-generated exci-ton pair characteristics matched the absorbance properties of the blended material and that the absorption and photocurrent characteristics of the respective components could be combined. This process for the heterogeneous blending of organic semiconductors has the potential to improve phototransistor performance and contribute to the development of broadband absorbing phototransistors.