Energy-efficient dispersion compensation for digital micromirror device.

Due to the wave nature of light, the diffraction pattern generated by an optical device is sensitive to the shift of wavelength. This fact significantly compromises the digital micromirror device (DMD) in applications, such as full-color holographic display and multi-color fluorescence microscopy. The existing dispersion compensation techniques for DMD involve adding diffractive elements, which causes a large amount of waste of optical energy. Here, we propose an energy-efficient dispersion compensation method, based on a dispersive prism, for DMD. This method simulates the diffraction pattern of the optical fields reflected from the DMD with an angular spectrum model. According to the simulation, a prism and a set of optical components are introduced to compensate for the angular dispersion of DMD-modulated optical fields. In the experiment, our method reduced the angular dispersion, between the 532 nm and 660 nm light beams, by a factor of ∼8.5.

High-fidelity multi-channel optical information transmission through scattering media.

High-fidelity optical information transmission through strongly scattering media is challenging, but is crucial for the applications such as the free-space optical communication in a haze or fog. Binarizing optical information can somehow suppress the disruptions caused by light scattering. However, this method gives a compromised communication throughput. Here, we propose high-fidelity multiplexing anti-scattering transmission (MAST). MAST encodes multiple bits into a complex-valued pattern, loads the complex-valued pattern to an optical field through modulation, and finally employs a scattering matrix-assisted retrieval technique to reconstruct the original information from the speckle patterns. In our demonstration, we multiplexed three channels and MAST achieved a high-fidelity transmission of 3072 (= 1024× 3) bits data per transmission and average transmission error as small as 0.06%.

Multi-view stitching phase measuring deflectometry for freeform specular surface metrology.

Phase measuring deflectometry (PMD) offers notable advantages for precision inspection of specular elements. Nevertheless, if confronts challenges when measuring freeform specular surfaces due to the dispersion of reflection rays from surfaces with high local slopes. Here, we propose a multi-view stitching PMD. It utilizes distinct sensors combining with a screen to capture the appearance of each region. After precisely calibrating the entire system to correct the absolute depth of each region, the appearances of all regions are precisely stitched together, reconstructing the comprehensive appearance of the surface. Through experimental setup, we measured the 3D morphology of a spherical lens with a curvature radius of 155.04 mm and a peak-to-valley (PV) value of 2.9 mm, which yielded a measurement accuracy of 5.3 µm (relative error: 0.18 %). Furthermore, we successfully measured the appearance of a curved mobile phone screen with local slopes ranging from -46.1° to 51.3°, and freeform acrylic sheet with local slopes ranging from -6.7° to 7.7° and a PV value of 5.3 mm.

High-frame-rate reconfigurable diffractive neural network based on superpixels.

The existing implementations of reconfigurable diffractive neural networks rely on both a liquid-crystal spatial light modulator and a digital micromirror device, which results in complexity in the alignment of the optical system and a constrained computational speed. Here, we propose a superpixel diffractive neural network that leverages solely a digital micromirror device to control the neuron bias and connection. This approach considerably simplifies the optical system and achieves a computational speed of 326 Hz per neural layer. We validate our method through experiments in digit classification, achieving an accuracy of 82.6%, and action recognition, attaining a perfect accuracy of 100%. Our findings demonstrate the effectiveness of the superpixel diffractive neural network in simplifying the optical system and enhancing computational speed, opening up new possibilities for real-time optical information processing applications.

Anti-scattering light focusing with full-polarization digital optical phase conjugation based on digital micromirror devices.

The high resolution of optical imaging and optogenetic stimulation in the deep tissue requires focusing light against strong scattering with high contrast. Digital optical phase conjugation (DOPC) has emerged recently as a promising solution for this requirement, because of its short latency. A digital micromirror device (DMD) in the implementation of DOPC enables a large number of modulation modes and a high speed of modulation both of which are important when dealing with a highly dynamic scattering medium. Here, we propose full-polarization DOPC (fpDOPC) in which two DMDs simultaneously modulate the two orthogonally polarized components of the optical field, respectively, to mitigate the effect of depolarization caused by strong scattering. We designed a simple system to overcome the difficulty of alignment encountered when modulating two polarized components independently. Our simulation and experiment showed that fpDOPC could generate a high-contrast focal spot, even though the polarization of light had been highly randomized by scattering. In comparison with the conventional method of modulating the polarization along a particular direction, fpDOPC can improve the peak to background ratio of the focal spot by a factor of two. This new technique has good potential in applications such as high-contrast light focusing in vivo.

Gradient-assisted focusing light through scattering media.

Focusing light through a scattering medium is a longstanding challenge in biomedical optics, to which wavefront shaping is a powerful solution. The state-of-the-art feedback-based approach is the widely used genetic algorithm method. However, it can only achieve relatively low enhancement of the focus, and the genetic algorithm is known to be time-consuming. To tackle those issues, we propose a gradient-assisted strategy for wavefront shaping. The proposed method conducts optimization in the function distribution space. Specifically, when optimizing the parameters along each iteration, the consequent function distribution changes within a distance as measured by the Kullback-Leibler divergence. Taking advantage of the gradient information, the proposed method is over 60× faster to obtain the same peak-to-background ratio (PBR) level. Compared with the genetic algorithm that is able to optimize a number of 64×64 phase segments, the proposed gradient strategy is able to optimize 256×256 phase segments, and gives 20× higher focus enhancement as quantified by the PBR.

The correlation between vitamin D, glucose homeostasis and androgen level among polycystic ovary syndrome patients: a cross-sectional study.

MATERIAL AND METHODS: A total of 290 women with PCOS participated in this cross-sectional study. Glucose homeostasis was assessed by a 75-g oral glucose tolerance test and the concentration of serum 25-hydroxy vitamin D was determined among all subjects. The homeostasis model assessment of insulin resistance (HOMA-IR) was taken as the indicator of insulin resistance. Beta cell function was estimated using the insulinogenic index and the disposition index. Free androgen index (FAI) was used to represent the androgen level. RESULTS: In our study, 7.2% of the patients had Vit D severe deficiency, 75.2% had Vit D deficiency and 15.5% had vit D insufficiency. The level of serum 25(OH)D showed a significant positive association with insulinogenic index (r = 0.147, p < .05), disposition index (r = 0.280, p < .05), and SHBG (r = 0.178, p < .05) but exhibited a negative association with HOMA-IR (r = -0.198, p < .05), FAI (r = -0.178, p < .05). Adjusted age and BMI, 25(OH)D would be the dependent variable on disposition index [B = 0.259, 95%CI(0.041,0.477)] and FAI [B = -0.125, 95%CI(-0.232, -0.017)]. CONCLUSIONS: According to our results, the low levels of serum 25(OH)D were common in women with PCOS, which was speculated to be associated with glucose homeostasis and the androgen level.

Intelligently optimized digital optical phase conjugation with particle swarm optimization.

Wavefront shaping (WFS) based on digital optical phase conjugation (DOPC) has gained major interest in focusing light through or inside scattering media. However, the quality of DOPC is greatly limited by imperfections of the system in a complicated and coupled way. In this Letter, we incorporate the concept of global optimization to solve this problem comprehensively for the first time, to the best of our knowledge. An automatic and intelligent optimization framework for DOPC techniques is proposed, leveraging the global optimization ability of particle swarm optimization (PSO). We demonstrate the general and powerful ability of the proposed approach in a series of DOPC-related experiments for focusing through and inside scattering media. This novel work can improve the OPC quality greatly and simplify the development of a high-performance DOPC system, which may open up a new avenue for the general scientific community to benefit from DOPC-based WFS in their potential applications.

Laser differential confocal interference multi-parameter comprehensive measurement method and its system for spherical lens.

Different measurement methods have been used to achieve different parameter measurements of a spherical lens, and multi-parameter measurements of a spherical lens have low measurement accuracy and efficiency. This paper proposes a new, laser differential confocal interference multi-parameter measurement (DCIMPM) method for spherical lens. Based on this proposed DCIMPM, a multi-parameter comprehensive measurement system is developed for spherical lens, which uses the laser differential confocal parameter measurement technique to measure the radius of curvature, thickness, and refractivity of spherical lens, and uses the laser interference measurement technique to measure the surface figure of a spherical lens. Therefore, the DCIMPM system, for the first time, achieves high-accuracy multi-parameter comprehensive measurements of a spherical lens on a single instrument. Experiments indicate that the developed DCIMPM system can achieve a measurement accuracy of 5 × 10-6 for the lens radius, 2.5 × 10-4 for the lens thickness, 2.2 × 10-4 for the lens refractivity, and a peak to valley of λ/20 for the surface figure of the lens. The proposed DCIMPM principle and developed system provide a new approach to achieve multi-parameter comprehensive measurements for spherical lens.

Laser differential confocal paraboloidal vertex radius measurement.

This Letter proposes a laser differential confocal paraboloidal vertex radius measurement (DCPRM) method for the high-accuracy measurement of the paraboloidal vertex radius of curvature. DCPRM constructs an autocollimation vertex radius measurement light path for the paraboloid by placing a reflector in the incidence light path. This technique is based on the principle that a paraboloid can aim a parallel beam at its focus without aberration and uses differential confocal positioning technology to identify the paraboloid focus and vertex accurately. Measurement of the precise distance between these two positions is achieved to determine the paraboloid vertex radius. Preliminary experimental results indicate that DCPRM has a relative expanded uncertainty of less than 0.001%.

Radius measurement by laser confocal technology.

A laser confocal radius measurement (LCRM) method is proposed for high-accuracy measurement of the radius of curvature (ROC). The LCRM uses the peak points of confocal response curves to identify the cat eye and confocal positions precisely. It then accurately measures the distance between these two positions to determine the ROC. The LCRM also uses conic fitting, which significantly enhances measurement accuracy by restraining the influences of environmental disturbance and system noise on the measurement results. The experimental results indicate that LCRM has a relative expanded uncertainty of less than 10 ppm for both convex and concave spheres. Thus, LCRM is a feasible method for ROC measurements with high accuracy and concise structures.

Erratum: Wavefront shaping improves the transparency of the scattering media: a review (Publisher's Note).

[This corrects the article DOI: 10.1117/1.JBO.29.S1.S11507.].

Wavefront shaping improves the transparency of the scattering media: a review.

Significance: Wavefront shaping (WFS) can compensate for distortions by optimizing the wavefront of the input light or reversing the transmission matrix of the media. It is a promising field of research. A thorough understanding of principles and developments of WFS is important for optical research. Aim: To provide insight into WFS for researchers who deal with scattering in biomedicine, imaging, and optical communication, our study summarizes the basic principles and methods of WFS and reviews recent progress. Approach: The basic principles, methods of WFS, and the latest applications of WFS in focusing, imaging, and multimode fiber (MMF) endoscopy are described. The practical challenges and prospects of future development are also discussed. Results: Data-driven learning-based methods are opening up new possibilities for WFS. High-resolution imaging through MMFs can support small-diameter endoscopy in the future. Conclusion: The rapid development of WFS over the past decade has shown that the best solution is not to avoid scattering but to find ways to correct it or even use it. WFS with faster speed, more optical modes, and more modulation degrees of freedom will continue to drive exciting developments in various fields.

Computational Imaging: The Next Revolution for Biophotonics and Biomedicine.

This Editorial is the preface for the topical collection of "Computational Imaging for Biophotonics and Biomedicine", which collates the 12 contributions listed in Table 1 [...].

Measuring the lens focal length by laser reflection-confocal technology.

A laser reflection-confocal focal-length measurement (LRCFM) is proposed for the high-accuracy measurement of lens focal length. LRCFM uses the peak points of confocal response curves to precisely identify the lens focus and vertex of the lens last surface. LRCFM then accurately measures the distance between the two positions to determine the lens focal length. LRCFM uses conic fitting, which significantly enhances measurement accuracy by inhibiting the influence of environmental disturbance and system noise on the measurement results. The experimental results indicate that LRCFM has a relative expanded uncertainty of less than 0.0015%. Compared with existing measurement methods, LRCFM has high accuracy and a concise structure. Thus, LRCFM is a feasible method for high-accuracy focal-length measurements.

Correlation Between Mean Amplitude of Glycemic Excursion and Bone Turnover Markers in Patients with Type 2 Diabetes: A Cross-Sectional Study.

Objective: The present study explores the relationship between glycemic excursion and bone turnover markers. Methods: A total of 250 patients with type 2 diabetes mellitus (T2DM) (142 female and 108 male patients) were enrolled in this study. All participants underwent 72 hours of continuous glycemic monitoring to evaluate the mean amplitude of glycemic excursions (MAGE) of each person. Bone turnover markers and other biochemical data were measured for each patient. Linear regression was performed to explore the relationship between bone turnover markers and glycemic excursion. A value of P < 0.05 was considered statistically significant. Results: MAGE was negatively correlated to N-terminal propeptide of type 1 collagen (P1NP) female: [odds ratios (95% confidence interval) (OR (95% CI)), -2.516 (-5.389, 0.356)]; male: [-2.895, (-6.521, -0.731)] and C-terminal telopeptide fragments of type-I collagen (ß-CTX) female [-0.025, (-0.036, 0.005)]; male [-0.043, (-0.082, 0.003)]. MAGE was still negatively correlated with ß-CTX female [-0.036, (-0.198, -0.030)]; male [-0.048, (-0.089, -0.007)] after adjusting for clinical data and biochemical indices. Conclusion: An independent negative relationship between glycemic excursion and bone turnover markers in patients with T2DM was identified in this study.

An ultrahigh-fidelity 3D holographic display using scattering to homogenize the angular spectrum.

A three-dimensional (3D) holographic display (3DHD) can preserve all the volumetric information about an object. However, the poor fidelity of 3DHD constrains its applications. Here, we present an ultrahigh-fidelity 3D holographic display that uses scattering for homogenization of angular spectrum. A scattering medium randomizes the incident photons and homogenizes the angular spectrum distribution. The redistributed field is recorded by a photopolymer film with numerous modulation modes and a half-wavelength scale pixel size. We have experimentally improved the contrast of a focal spot to 6 × 106 and tightened its spatial resolution to 0.5 micrometers, respectively ~300 and 4.4 times better than digital approaches. By exploiting the spatial multiplexing ability of the photopolymer and the transmission channel selection capability of the scattering medium, we have realized a dynamic holographic display of 3D spirals consisting of 20 foci across 1 millimeter × 1 millimeter × 26 millimeters with uniform intensity.

Resource scarcity aggravates ingroup bias: Neural mechanisms and cross-scenario validation.

Previous studies examining the relationship between ingroup bias and resource scarcity have produced heterogeneous findings, possibly due to their focus on the allocation of positive resources (e.g. money). This study aims to investigate whether ingroup bias would be amplified or eliminated when perceived survival resources for counteracting negative stimuli are scarce. For this purpose, we exposed the participants and another confederate of the experimenters (ingroup/outgroup member) to a potential threat of unpleasant noise. Participants received some 'relieving resources' to counteract noise administration, the amount of which may or may not be enough for them and the confederate in different conditions (i.e. abundance vs. scarcity). First, a behavioural experiment demonstrated that intergroup discrimination manifested only in the scarcity condition; in contrast, the participants allocated similar amounts of resource to ingroup and outgroup members in the abundance condition, indicating a context-dependent allocation strategy. This behavioural pattern was replicated in a follow-up neuroimaging experiment, which further revealed that when contrasting scarcity with abundance, there was higher activation in the anterior cingulate cortex (ACC) as well as stronger functional connectivity of the ACC with the empathy network (including the temporoparietal junction and medial prefrontal cortex) for ingroup compared to outgroup members. We suggest that ACC activation reflects the mentalizing process toward ingroup over outgroup members in the scarcity condition. Finally, the ACC activation level significantly predicted the influence of resource scarcity on ingroup bias in hypothetical real-life situations according to a follow-up examination.

Laser differential reflection-confocal focal-length measurement.

A new laser differential reflection-confocal focal-length measurement (DRCFM) method is proposed for the high-accuracy measurement of the lens focal length. DRCFM uses weak light reflected from the lens last surface to determine the vertex position of this surface. Differential confocal technology is then used to identify precisely the lens focus and vertex of the lens last surface, thereby enabling the precise measurement of the lens focal length. Compared with existing measurement methods, DRCFM has high accuracy and strong anti-interference capability. Theoretical analyses and experimental results indicate that the DRCFM relative measurement error is less than 10 ppm.

Laser differential confocal radius measurement system.

A laser differential confocal radius measurement system with high measurement accuracy is developed for optical manufacturing and metrology. The system uses the zero-crossing point of the differential confocal intensity curve to precisely identify the cat's-eye and confocal positions and uses an interferometer to measure the distance between these two positions, thereby achieving a high-precision measurement for the radius of curvature. The coaxial measuring optical path reduces the Abbe error, and the air-bearing slider reduces the motion error. The error analysis indicates the theoretical accuracy of the system is up to 2 ppm, and the experiment shows that the system has high focusing sensitivity and is little affected by environmental fluctuations; the measuring repeatability is between 4 and 12 ppm.