Development of a metrological reference system for the form measurement of aspheres and freeform surfaces based on a tilted-wave interferometer

Aspheres and freeform surfaces play an important role in today's optics industry. However, the measurement of such complex surfaces is still challenging even with state-of-the-art manufacturing technology, and there is an urgent need in industry for a non-contact, highly accurate reference measurement technique. To meet this demand, at PTB, a metrological reference system for the contact-free form measurement of aspheres and freeform surfaces is under development. The measurement system is based on a tilted-wave interferometer. Advances in computational capabilities have made it possible to solve the complex inverse problems associated with this measurement system and to develop sophisticated analysis procedures for reconstructing the surface under test from the measured interferogram data. In this paper, we will present the status of the tilted-wave interferometer-based measurement system at PTB, describe the analysis procedures we have designed and show initial measurement results. The benefit of the implementation presented here is that it allows insight to be gained into the performance of the measurement system and enables traceable measurements to be established with low uncertainty.

The Effects of Concussion on Quantity and Quality of Sleep in Football Athletes

ObjectiveThe objective was to observe the quantity and quality of sleep of collegiate athletes following a concussion.BackgroundPatients diagnosed with a concussion report a disruption or change in their sleep with 46% of patients still having sleep disturbances 3 months after the event. Research is lacking on the sleep disruption or sleep changes in athletes who have experienced a concussion.Design/MethodsThis IRB-approved convenient cohort study involved athletes from 2 local universities. 27 (20 non-concussed and 7 concussed) male collegiate football players (19.93 ± 1.14 years old, 1.82 ± 0.08 m, and 96.42 ± 21.26 kg) wore a Readiband device for 7–10 days or throughout concussion recovery. Concussed participants completed a symptom score sheet each day. Participants returned the Readiband device and completed the Pittsburgh Sleep Quality Index Questionnaire (PSQIQ) after 7–10 days or on return to play. The sleep parameters, and PSQIQ scores were analyzed using non-parametric & independent t-tests with the alpha level set at 0.05.ResultsThe t-tests indicated a difference between the total minutes in bed at the initial measurement (F = 11.839, df = 1, p = 0.037) between the concussed (353.29 ± 110.48 minutes) and non-concussed (471.5 ± 125.09 minutes) groups. There was also a difference between the total minutes asleep at the initial measurement (F = 12.662, df = 1, p = 0.032) between the concussed (286.43 ± 86.73) and non-concussed groups (383.7 ± 104.86). The last measurement that indicated a difference was the calculated minutes in bed at the initial measurement (F = 11.916, df = 1, p = 0.023) between the concussed (326.4 3 ± 97.01) and non-concussed groups (441.60 ± 110.55).ConclusionsThe study results indicate that concussion affects the quantity of sleep, with concussed athletes spending less time in bed and fewer minutes asleep. Changes in sleep occur post-concussion, which may delay concussion recovery.

Surface Measurement of a Large Inflatable Reflector in Cryogenic Vacuum

The metrology of membrane structures, especially inflatable, curved, optical surfaces, remains challenging. Internal pressure, mechanical membrane properties, and circumferential boundary conditions imbue highly dynamic slopes to the final optic surface. Here, we present our method and experimental results for measuring a 1 m inflatable reflector’s shape response to dynamic perturbations in a thermal vacuum chamber. Our method uses phase-measuring deflectometry to track shape change in response to pressure change, thermal gradient, and controlled puncture. We use an initial measurement as a virtual null reference, allowing us to compare 500 mm of measurable aperture of the concave f/2, 1-meter diameter inflatable optic. We built a custom deflectometer that attaches to the TVAC window to make full use of its clear aperture, with kinematic references behind the test article for calibration. Our method produces 500 × 500 pixel resolution 3D surface maps with a repeatability of 150 nm RMS within a cryogenic vacuum environment (T = 140 K, P = 0.11 Pa).

Effects of a preparatory training protocol on the movement and body stability of handball players

Handball is a sport with a high risk of injury, The prevalence of injury is only obtainable through a thorough and comprehensive analysis. One of the most commonly used test batteries for interpreting the characteristics of an injury is the Functional Movement Screen (FMSTM). It makes possible to possible to identify movement limitations and asymmetries which are believed to impact injury risk in sports. The aim of this study is to use the FMSTM to determine whether an eight-week training protocol can predict and prevent injuries in handball. The study sample comprised the fifteen members of the Borac handball club youth team. The initial measurement showed that most players (80%) had an overall score in the test battery ranging from 15 to 20 points. In addition, three players were found to have asymmetry. Only one of the three players had an overall score in the FMSTM of ≤14. The participants scored the lowest in the initial measurement for Rotary Stability, followed by Deep Squat and Hurdle Step Left. They scored the highest in the Shoulder Mobility. After the implementation of the exercise protocol for improving body mobility and stability, the final measurements showed that all the participants had an overall score in the FMSTM of >14. The value of eta squared showed that training in between the two measurements had a significant impact. At the time of testing and protocol implementation no players sustained any injuries during matches or in training. This study confirmed that the FMSTM can be used to predict injuries in sports.

Adaptive Block-Based Compressed Video Sensing Based on Saliency Detection and Side Information

The setting of the measurement number for each block is very important for a block-based compressed sensing system. However, in practical applications, we only have the initial measurement results of the original signal on the sampling side instead of the original signal itself, therefore, we cannot directly allocate the appropriate measurement number for each block without the sparsity of the original signal. To solve this problem, we propose an adaptive block-based compressed video sensing scheme based on saliency detection and side information. According to the Johnson–Lindenstrauss lemma, we can use the initial measurement results to perform saliency detection and then obtain the saliency value for each block. Meanwhile, a side information frame which is an estimate of the current frame is generated on the reconstruction side by the proposed probability fusion model, and the significant coefficient proportion of each block is estimated through the side information frame. Both the saliency value and significant coefficient proportion can reflect the sparsity of the block. Finally, these two estimates of block sparsity are fused, so that we can simultaneously use intra-frame and inter-frame correlation for block sparsity estimation. Then the measurement number of each block can be allocated according to the fusion sparsity. Besides, we propose a global recovery model based on weighting, which can reduce the block effect of reconstructed frames. The experimental results show that, compared with existing schemes, the proposed scheme can achieve a significant improvement in peak signal-to-noise ratio (PSNR) at the same sampling rate.

Twins Are Always Serving Science, What About Their Own Needs? Twins’ Need for Social Anxiety Program

Objective: The effectiveness of the Social Anxiety Program on Adolescent Twins investigated in this study. Method: The study is a mixed-method study using a one-group pretest-posttest design, together with the qualitative method. First, Intraclass Correlation Coefficient used to find out the concordance and differentiation level of the twins’ social anxiety. Because monozygotic twins’ concordance rate is higher than dizygotic twins, four pair female monozygotic twins aged 17-18 participated in the group. Wilcoxon Single Ranks Test used to analyze the experimental part of the research. Three sessions of focus groups held after the program. Content analysis techniques used as a qualitative analysis. Result: As a result, there was a statistically significant difference between pre/post-program. Since this difference was in favor of initial measurement, the program interpreted as being effective. Themes also supported the quantitative results. Conclusion: Findings obtained from both experimental and qualitative parts discussed. Suggestions provided for future researcher.

Fiber Optic Based Distributed Mechanical Vibration Sensing

The distributed long-range sensing system, using the standard telecommunication single-mode optical fiber for the distributed sensing of mechanical vibrations, is described. Various events generating vibrations, such as a walking or running person, moving car, train, and many other vibration sources, can be detected, localized, and classified. The sensor is based on phase-sensitive optical time-domain reflectometry (ϕ-OTDR). Related sensing system components were designed and constructed, and the system was tested both in the laboratory and in the real deployment, with an 88 km telecom optical link, and the results are presented in this paper. A two-fiber sensor unit, with a double-sensing range was also designed, and its scheme is described. The unit was constructed and the initial measurement results are presented.

Anterior chamber changes assessment by Scheimpflug analysis after intravitreal dexamethasone implantation

Purpose: To evaluate structural changes in the anterior chamber and intraocular pressure (IOP) changes following intravitreal dexamethasone implantation. Methods: Forty-two eyes of 42 patients that received intravitreal dexamethasone implant for the management of macular edema secondary to diabetic retinopathy or branch retinal vein occlusion (BRVO) were included in the study. IOP was measured by Goldmann applanation tonometry. Anterior chamber depth (ACD) and iridocorneal angle (ICA) was measured by a Scheimflug camera (Sirius, CSO, Italy) the day before the injection of the dexamethasone implant and on postoperative day 1, first week, and first month. Results: Mean IOP was 15.14 ± 2.77 mmHg before the procedure and, 15.67 ± 3.70 mmHg, 15.86 ± 3.11 mmHg, 16.21 ± 2.75 mmHg on day 1, first week, and first month following intravitreal dexamethasone implantation, respectively. Mean ICA and ACD were significantly higher in pseudophakic eyes compared to phakic eyes. However, there was no statistically significant change in ICA before and after the procedure (on postoperative day 1, first week, and first month) among both phakic and pseudophakic patients ( p = 0.783). Similarly, ACD remained unchanged after the procedure (on postoperative day 1, first week, and first month) compared to the initial measurement ( p = 0.802). Conclusion: This study confirmed that there was an increase in IOP. However, these changes were not accompanied with a change in ACD or ICA.