Spectral origami: an angle-variable, wavelength-selective concept with a highly efficient filter-based sensing.

This study demonstrates the concept of an angle-variable compact spectral module. As a key feature, the filter-based module enables highly efficient wavelength-selective light detection by applying the reflective beam path according to the origami example. It was accomplished through inclined mirrors, which allow for different incident angles on the wavelength separating interference filters used in a robust assembly with no moving parts. To experimentally verify the concept, a wavelength range between 550 and 700 nm was detected by 11 spectral channels. These initial results showed the potential to develop easily scalable and application-tailored sensors, which can overcome conventional filter-based sensor approaches that use upright or fixed-angle illumination.

Advanced linear axial wavelength spreading through cascaded double hyperchromats.

This study explores the design and optimization of cascaded double-hyperchromatic optical systems (i.e., 2×2 lenses), focusing on achieving an extremely linear axial spectral decomposition characterized by an exceptionally low equivalent Abbe number. The investigation involves two double hyperchromats, considering both purely refractive systems and hybrid configurations that combine refractive and diffractive elements. For purely refractive systems, alternating focal length signs of divergent and collective lenses are crucial to achieve significant axial chromatic dispersion. In hybrid systems, the position of the diffractive optical element (DOE) and the selection of focal lengths play key roles in obtaining extremely low equivalent Abbe numbers. The optimized systems demonstrate absolute equivalent Abbe numbers of 0.983 for purely refractive and 0.65 for hybrid systems-more than four times lower than the absolute Abbe number of a single diffractive element. Notably, even systems using standard materials exhibit significantly low equivalent Abbe numbers of 2.5 and 1.4 for pure refractive and hybrid configurations, respectively. These results offer promising opportunities for improving optical applications based on axial spectral decomposition, overcoming previous limitations of axial chromatic spreading.

Assessing menopause symptoms in women with traumatic brain injury: the development and initial testing of a new scale.

With greater survival rates after catastrophic injury, more women with traumatic brain injury (TBI) are living longer than ever. However, knowledge about this transition in these women is largely unexamined and there are no scales that have been developed to assess the experience of symptoms. To address this gap, we developed and tested a new scale of menopause symptoms in midlife women with TBI. We selected candidate items from two existing measures based on feedback from focus group discussions with seven women with TBI. Twenty candidate items were tested in cognitive interviews with six women with TBI/1 non-TBI. Then, these were field tested with 221 participants (TBI, n = 68; non-TBI, n = 153) recruited from registries. Rasch analysis and convergent validity testing were used to evaluate the new scale. Results of the Rasch analysis indicate that overall, the scale fits well the Rasch model with evidence for unidimensionality. Differential item functioning indicated that the scale performed equally well for women with and without TBI and distinguished pre- and post-menopausal states. Convergent validity was found in the expected directions. These findings support further development of the new scale to understand the experience of menopause symptoms among women with TBI.

Tailored chromatic diffraction efficiency of double-layer single-relief blazed gratings.

"Wavelength selectivity" is an important intrinsic property of diffractive optical elements that offers significant application potential. Here, we focus on tailored wavelength selectivity, the controlled efficiency distribution into different specific diffraction orders for selected wavelengths or wavelength ranges from UV to IR using interlaced double-layer single-relief blazed gratings composed of two materials. Dispersion characteristics of inorganic glasses, layer materials, polymers, nanocomposites, and high-index liquids are taken into account to investigate the impact of especially intersecting or partially overlapping dispersion curves on diffraction efficiency in different orders, providing a guideline for material choice depending on the required optical performance. By selecting appropriate combinations of materials and adjusting the grating depth, a wide variety of small or large wavelength ranges can be assigned to different diffraction orders with high efficiency that can be beneficially applied to wavelength selective functions in optical systems also including imaging or broadband lighting applications.

Catadioptric sensor concept with interlaced beam paths for imaging and pinpoint spectroscopy.

This paper presents the concept, optical design, and implementation of a catadioptric sensor for simultaneous imaging of a scene and pinpoint spectroscopy of a selected position, with object distances ranging from tens of centimeters to infinity and from narrow to wide adjustable viewing angles. The use of reflective imaging elements allows the implementation of folded and interlaced beam paths for spectroscopy and image acquisition, which enables a compact setup with a footprint of approximately 90m m×80m m. Although the wavelength range addressed extends far beyond the visible spectrum and reaches into the near infrared (∼400n m to 1000 nm), only three spherical surfaces are needed to project the intermediate image onto the image detector. The anamorphic imaging introduced by the folded beam path with different magnification factors in the horizontal and vertical directions as well as distortion can be compensated by software-based image processing. The area of the scene to be spectrally analyzed is imaged onto the input of an integrated miniature spectrometer. The imaging properties and spectroscopic characteristics are demonstrated in scenarios close to potential applications such as product sorting and fruit quality control.

Crash Risk Following Return to Driving After Moderate-to-Severe TBI: A TBI Model Systems Study.

OBJECTIVE: To examine motor vehicle crash frequency and risk factors following moderate-to-severe traumatic brain injury (TBI). SETTING: Eight TBI Model Systems sites. Participants: Adults ( N = 438) with TBI who required inpatient acute rehabilitation. DESIGN: Cross-sectional, observational design. MAIN MEASURES: Driving survey completed at phone follow-up 1 to 30 years after injury. RESULTS: TBI participants reported 1.5 to 2.5 times the frequency of crashes noted in the general population depending on the time frame queried, even when accounting for unreported crashes. Most reported having no crashes; for those who experienced a crash, half of them reported a single incident. Based on logistic regression, age at survey, years since injury, and perception of driving skills were significantly associated with crashes. CONCLUSION: Compared with national statistics, crash risk is higher following TBI based on self-report. Older age and less time since resuming driving were associated with lower crash risk. When driving was resumed was not associated with crash risk. These results do not justify restricting people from driving after TBI, given that the most who resumed driving did not report experiencing any crashes. However, there is a need to identify and address factors that increase crash risk after TBI.

Compact double-pass Echelle spectrometer employing a crossed diffraction grating.

This contribution presents the design and implementation of a compact and robust Echelle-inspired cross-grating spectrometer which is arranged as a double pass setup. This allows use of the employed refractive elements for collimation of the incoming light and, after diffraction at the reflective crossed diffraction grating, for imaging the diffracted light onto the detector. The crossed diffraction grating combines the two dispersive functionalities of a classical Echelle spectrometer in a single element and is therefore formed by a superposition of two blazed linear gratings which are oriented perpendicularly. The refractive elements and the plane grating are arranged in a rigid objective group which is beneficial in terms of stability and robustness. The experimental tests prove that the designed resolving power of more than 300 is achieved for the addressed spectrum ranging from 400 nm to 1100 nm by using an entrance pinhole diameter of 105 µm. The utilization of a single mode fiber increases the resolving power to more than 1000, but leads to longer acquisition times.

Hyperchromatic lens doublets with an extremely small equivalent Abbe number employing diffractive elements and refractive materials with exceptional dispersion properties.

Hyperchromatic systems are characterized by strong longitudinal chromatic aberrations that are quantitatively described by very small equivalent Abbe numbers. In this contribution, doublet systems are systematically studied with the aim of obtaining extreme values for the equivalent Abbe numbers. Both purely refractive combinations and hybrid systems of diffractive and refractive components are considered. Chromatic axial splitting is determined as a function of the optical powers of the individual components as well as the dispersion properties of the materials involved. In order to determine actual implementable configurations for extremely small equivalent Abbe numbers, a systematic ray-trace analysis is performed in addition to paraxial studies, taking into account geometric constraints on lens curvatures and considering also complete, continuous dispersion curves. As extreme values for systems with appropriate imaging quality, an equivalent Abbe number of υ~=-2.5 is obtained for the purely refractive approach, and υ~=0.4 for the hybrid case, which is more than 8 times smaller than the absolute value of a single diffractive lens.

Variable ring-shaped lithography for the fabrication of meso- and microscale binary optical elements.

This paper presents concept, optical design, and the implementation of a novel, to the best of our knowledge, lithographic exposure tool for the fabrication of rotationally symmetric meso- and microscale optical structures using a variable ring-shaped light distribution. Compared to the conventional lithographic technique of direct writing in Cartesian coordinates, which is intrinsically suboptimal for the fabrication of rotationally symmetric optical structures, this approach allows for fast exposure and avoids disturbing stitching effects. The diameter of the exposure ring varies between 1.6 and 6.5 mm, and the ring width measures ∼75µm full width at half-maximum for all diameters. The basic capabilities of the exposure tool are demonstrated by the fabrication of exemplary meso- and microscale structures such as diffractive axicon elements, phase rings, Fresnel zone plates and zone plate arrays.

Folded beam path architecture for highly efficient filter-based spectral sensors.

This paper demonstrates a method to significantly enhance the detection efficiency of filter-based spectral sensors without the use of additional dichroic optics for spectral preselection. The fundamental principle is that light reflected from one interference filter or filter segment can be used consecutively, reducing the overall system losses. The proof-of-concept is presented using two compact optical modules. The first module uses 10 individual filters between 520 and 800 nm, and the second is capable of continuous spectrum acquisition between 450 and 825 nm using a linear variable filter (LVF) as a key element. An efficiency increase factor of up to approximately 100 compared to a common system, where the entire LVF is directly illuminated, was demonstrated.

Multi-aperture system approach for snapshot multispectral imaging applications.

We present an ultra-compact system approach for snapshot, multispectral imaging. It is based on a slanted linear variable spectral filter mounted in close proximity to the entrance pupil of a micro-optical, multi-aperture imaging system. A compact demonstration setup with a size of only 60 × 60 × 28 mm3 is developed, which enables the acquisition of 66 spectral channels in a single shot and offers a linear spectral sampling of approximately six nanometers over an extended wavelength range of 450-850 nm. The spatial sampling of each channel covers up to 400 × 400 pixels. First, the concept, the optical design and the fabrication are detailed. After the optical performance characterization, a comprehensive calibration strategy is developed and applied. An experimental demonstration is performed by acquiring the spatial and the spectral information of an imaged test scene.

Return to Driving After Moderate-to-Severe Traumatic Brain Injury: A Traumatic Brain Injury Model System Study.

OBJECTIVE: Describe who is able to return to driving (RTD) after moderate-to-severe traumatic brain injury (TBI), when this occurs, who maintains that activity, and the association with outcome. DESIGN: Cross-sectional descriptive study. SETTING: Eight follow-up sites of the TBI Model Systems (TBIMS) program. PARTICIPANTS: 618 participants enrolled in the TBIMS and 88 caregivers (N=706). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: A survey was completed from 1-30 years postinjury focusing on RTD. Descriptors included demographic information, injury severity, and current employment status. Outcome was assessed at the time of the interview, including depression, quality of life, functional status, and community participation. RESULTS: Of 706 respondents, 78% (N = 552) RTD, but 14% (N = 77) of these did not maintain that activity. Of those who RTD, 43% (N = 192) did so within 6 months of the injury and 92% did so within 24 months postinjury. The percentage of people driving after TBI did not differ significantly based on age at time of injury or follow-up. There were significant differences between drivers and nondrivers with respect to severity of injury, seizures, race, education, employment, rural vs urban setting, marital status, and family income. We performed a multivariate logistic regression to examine the association between driving status and demographic variables, adjusting for other variables in the model. The strongest associations were with current employment, family income, race, seizures, and severity of injury. Driving was associated with greater community participation, better functional outcomes, fewer symptoms of depression, and greater life satisfaction. CONCLUSIONS: Over a span of 30 years, three-quarters of people experiencing moderate-to-severe TBI return to driving a personal vehicle, although not everyone maintains this activity. Employment, race, family income, and seizures are strongly associated with RTD.

Driving patterns, confidence, and perception of abilities following moderate to severe traumatic brain injury: a TBI model system study.

OBJECTIVE: Describe driving patterns following moderate-to-severe traumatic brain injury (TBI). Participants: Adults (N = 438) with TBI that required inpatient acute rehabilitation who had resumed driving. DESIGN: Cross-sectional, observational design. SETTING: Eight TBI Model System sites. MAIN MEASURES: A driving survey was completed at phone follow-up. RESULTS: Most respondents reported driving daily, although 41% reported driving less than before their injury. Driving patterns were primarily associated with employment, family income, sex, residence, and time since injury, but not injury severity. Confidence in driving was high for most participants and was associated with a perception that the TBI had not diminished driving ability. Lower confidence and perceived loss of ability were associated with altered driving patterns. CONCLUSION: Most people with moderate-to-severe TBI resume driving but perhaps not at pre-injury or normal levels compared to healthy drivers. Some driving situations are restricted. The relationship between low confidence/perceived loss of ability and driving patterns/restrictions suggests people with TBI are exhibiting some degree of caution consistent with those perceptions. Careful assessment of driving skills and monitoring during early stages of RTD is warranted, particularly for younger, male, and/or single drivers who express higher levels of confidence.

Factors Increasing Risk of Suicide after Traumatic Brain Injury: A State-of-the-Science Review of Military and Civilian Studies.

Primary Objective: Survey TBI literature to identify evidence of risk for post-injury suicide.Literature Selection: Search terms ((traumatic brain injury OR TBI) AND (suicidality OR suicidal behaviour OR suicidal ideation)) entered in PubMed, OVID Medline, PsychInfo, and Web of Science for papers published in print 01/01/1997 to 06/30/2019.Analysis of Literature: Authors screened abstracts, excluding duplicates and articles not meeting inclusion/exclusion criteria. Full papers were reviewed to make final exclusions. Data were extracted from 40 papers included co- and premorbid disorders, demographics, injury-related and psychological factors.Results: Persons with TBI have a higher risk for suicide than the general population. Reviewed articles reported comorbid depression and/or PTSD as risk factors for post-TBI suicide. Co- or premorbid substance misuse, sex, and sleep disturbance moderate risk. Quality of the literature was limited by sample size, the predominance of male participants, and inconsistency in reporting of findings.Conclusions: Comorbid depression and PTSD are significant post-TBI risk factors for suicide. Several variables combine to moderate or mediate TBI's connection with suicide. Civilian and military clinician cross-talk and consistent reporting of results from reproducible studies of post-TBI suicide risk factors could improve prevention and treatment efforts in veterans and civilians.

Black and white fused silica: modified sol-gel process combined with moth-eye structuring for highly absorbing and diffuse reflecting SiO2 glass.

Diffuse reflecting (white) and highly absorbing (black) fused silica based materials are presented, which combine volume modified substrates and surfaces equipped with anti-reflective moth-eye-structures. For diffuse reflection, micrometer sized cavities are created in bulk fused silica during a sol-gel process. In contrast, carbon black particles are added to get the highly absorbing material. The moth-eye-structures are prepared by block copolymer micelle nanolithography (BCML), followed by a reactive-ion-etching (RIE) step. The moth-eye-structures drastically reduce the specular reflectance on both diffuse reflecting and highly absorbing samples across a wide spectral range from 250 nm to 2500 nm and for varying incidence angles. The adjustment of the height of the moth-eye-structures allows us to select the spectral position of the specular reflectance minimum, which measures less than 0.1%. Diffuse Lambertian-like scattering and absorbance appear nearly uniform across the selected spectral range, showing a slight decrease with increasing wavelength.

Barriers to eating are associated with poor physical function in older women.

Older adults have physical and social barriers to eating but whether this affects functional status is unknown. We examined associations between eating barriers and physical function in the Women's Health Initiative (WHI). In 2012-14, a subset of alive and participating women (n = 5910) completed an in-home examination including the Short Physical Performance Battery (SPPB) (grip strength, balance, timed walking speed, chair stand). WHI participants complete annual mailed questionnaires; the 2013-14 questionnaire included items on eating alone, eating < two meals/day, dentition problems affecting eating, physical difficulties with cooking/shopping and monetary resources for food. Linear regression tested associations of these eating barriers with SPPB, adjusting for BMI, age, race/ethnicity, and medical multimorbidities. Over half (56.8%) of participants were ≥ 75 years, 98.8% had a BMI ≥ 25.0 kg/m2 and 66% had multimorbidities. Eating barriers, excluding eating alone, were associated with significantly lower total (all p < .001) and component-specific, multivariate-adjusted SPPB scores (all p < .05). Compared to no barriers, eating < two meals/day (7.83 vs. 8.38, p < .0002), dentition problems (7.69 vs. 8.38, p < .0001), inability to shop/prepare meals (7.74 vs. 8.38, p < .0001) and insufficient resources (7.84 vs. 8.37 p < .001) were significantly associated with multivariate-adjusted mean SPPB score < 8. Models additionally adjusting for Healthy Eating Index-2010 had little influence on scores. As barriers increased, scores declined further for grip strength (16.10 kg for 4-5 barriers, p = .001), timed walk (0.58 m/s for 4-5 barriers, p = .001) and total SPPB (7.27 for 4-5 barriers, p < .0001). In conclusion, in this WHI subset, eating barriers were associated with poor SPPB scores.

Structured metal double-blazed dispersion grating for broadband spectral efficiency achromatization.

The majority of spectrometers use reflective dispersion gratings with a metal-coated blazed grating profile for spectral decomposition. They achieve high diffraction efficiency at the design wavelength, which decays considerably in the adjacent longer and shorter wavelength ranges. We introduce a structured metal double-blazed grating with a high diffraction efficiency for a broadband spectral range, consisting of a sawtooth-like structured metal surface filled with a first dielectric transparent material. The planarized upper surface is covered with a second blazed profile of a different transparent material. We present a systematical theoretical analysis of the diffraction efficiency in reflection geometry, based on a scalar approach involving fundamental dispersion parameters such as Abbe numbers and relative partial dispersions of the materials. We find material combinations reducing the profile heights down to 1-2 µm.

Substantial increase in detection efficiency for filter array-based spectral sensors.

A method that significantly increases the detection efficiency of filter array-based spectral sensors is proposed. The basic concept involves a wavelength-dependent redistribution of incident light before it reaches the filter elements located in front of the detector. Due to this redistribution, each filter element of the array receives a spatially concentrated amount of a pre-selected and adjusted spectral partition of the entire incident light. This approach can be employed to significantly reduce the reflection and absorption losses of each filter element. The proof-of-concept is demonstrated by a setup that combines a series of consecutively arranged dichroic filters with Fabry-Perot filter arrays. Experimentally, an efficiency increase by a factor larger than 4 compared to a reference system is demonstrated. The optical system is a non-imaging spectrometer, which combines the efficiency enhancement module with the filter arrays, is compact (17.5mm×17.5mm×7.8mm), and integrated completely inside the CCD camera mount.

Realization of a compact cross-grating spectrometer and validating experimental tests.

Echelle inspired cross-grating spectrometers offer the potential to bridge the gap between classical high-end echelle spectrometers and curved-grating single-element instruments. In particular, the cross-grating approach offers the possibility to simultaneously achieve a high spectral resolution and a wide accessible spectral range in compact dimensions and without moving parts. We report on the complete realization and implementation details of an all-reflective cross-grating spectrometer based on a modified Czerny-Turner configuration including a folded beam path and a toric-convex mirror for aberration compensation. The applicability of the cross-grating spectrometer is demonstrated by test measurements including the recording of the spectra of different plant leaves. For the cross-grating spectrometer, with an accessible wavelength range between 330 and 1100 nm, a spectral resolution of 0.6 nm at 589 nm was achieved.

Various cross-linking methods inhibit the collagenase I degradation of rabbit scleral tissue.

BACKGROUND: Collagen cross-linking of the sclera is a promising approach to strengthen scleral rigidity and thus to inhibit eye growth in progressive myopia. Additionally, cross-linking might inhibit degrading processes in idiopathic melting or in ocular inflammatory diseases of the sclera. Different cross-linking treatments were tested to increase resistance to enzymatic degradation of the rabbit sclera. METHODS: Scleral patches from rabbit eyes were cross-linked using paraformaldehyde, glutaraldehyde or riboflavin combined with UV-A-light or with blue light. The patches were incubated with collagenase I (MMP1) for various durations up to 24 h to elucidate differences in scleral resistance to enzymatic degradation. Degraded protein components in the supernatant were detected and quantified using measurements of Fluoraldehyde o-Phthaldialdehyde (OPA) fluorescence. RESULTS: All cross-linking methods reduced the enzymatic degradation of rabbit scleral tissue by MMP1. Incubation with glutaraldehyde (1%) and paraformaldehyde (4%) caused nearly a complete inhibition of enzymatic degradation (down to 7% ± 2.8 of digested protein compared to control). Cross-linking with riboflavin/UV-A-light reduced the degradation by MMP1 to 62% ± 12.7 after 24 h. Cross-linking with riboflavin/blue light reduced the degradation by MMP1 to 77% ± 13.5 after 24 h. No significant differences could be detected comparing different light intensities, light exposure times or riboflavin concentrations. CONCLUSIONS: The application of all cross-linking methods increased the resistance of rabbit scleral tissue to MMP1-degradation. Especially, gentle cross-linking with riboflavin and UV-A or blue light might be a clinical approach in future.