Illumination Mode Research Articles

The impact of building surface optimization and dynamic control on climate adaptation

This study designed a simple residential unit model with dynamic climate-adaptive building skins and developed five skin control modes to analyse their impact on building climate adaptability. The main purpose of this study is to design building skin schemes and control modes with better climate adaptability. The experimental results show that the illumination and humidity control effect of the illumination mode group is the best, and its temperature control performance is also relatively good. It is the scheme with the best overall control performance. Its comfortable illumination time ratio and comfortable humidity time ratio are 65.2 and 76.3%, respectively, which are significantly higher than those of the other schemes. The absolute differences between the average room temperature and target temperature median values in the illumination mode group are 25.7 and 1.7°C, respectively, with minimal differences in temperature control effects compared with those of the other experimental groups. The experimental results indicate that controlling the opening and closing angles of building louvres according to the illumination of solar radiation can maximise the dynamic climate adaptability of the building. The results of this study will provide some useful references for improving the climate adaptability of civil buildings.

Unsupervised adaptive coded illumination Fourier ptychographic microscopy based on a physical neural network.

Fourier Ptychographic Microscopy (FPM) is a computational technique that achieves a large space-bandwidth product imaging. It addresses the challenge of balancing a large field of view and high resolution by fusing information from multiple images taken with varying illumination angles. Nevertheless, conventional FPM framework always suffers from long acquisition time and a heavy computational burden. In this paper, we propose a novel physical neural network that generates an adaptive illumination mode by incorporating temporally-encoded illumination modes as a distinct layer, aiming to improve the acquisition and calculation efficiency. Both simulations and experiments have been conducted to validate the feasibility and effectiveness of the proposed method. It is worth mentioning that, unlike previous works that obtain the intensity of a multiplexed illumination by post-combination of each sequentially illuminated and obtained low-resolution images, our experimental data is captured directly by turning on multiple LEDs with a coded illumination pattern. Our method has exhibited state-of-the-art performance in terms of both detail fidelity and imaging velocity when assessed through a multitude of evaluative aspects.

EFFECT OF DIFFERENT LIGHT INTENSITIES ON GROWTH AND DEVELOPMENT OF ARTEMIA (ARTEMIA SALINA) IN AN ARTIFICIAL ECOSYSTEM

Artemia nauplii are the best initital food for most fish larvae. Feeder fish, Artemia nauplii, contain the ingredients necessary for the survival of aquatic organisms during critical periods of early postembryonic ontogenesis. Thus, it is important to improve the biotechnology of Artemia cultivation in artificial ecosystems.
 Materials and Methods. In the course of the study, various illumination modes were used, namely, 1.5; 2.5 and 4 klx to determine the most effective one.
 Results. Various illumination modes affect Artemia development in different ways. The most effective illumination mode at the stage of embryonic development and the initial stages of postembryonic ontogenesis was 4 klx.

A Review of Advanced Transceiver Technologies in Visible Light Communications

Visible Light Communication (VLC) is an emerging technology that utilizes light-emitting diodes (LEDs) for both indoor illumination and wireless communications. It has the potential to enhance the existing WiFi network and connect a large number of high-speed internet users in future smart home environments. Over the past two decades, VLC techniques have made significant strides, resulting in transmission data rates increasing from just a few Mbps to several tens of Gbps. These achievements can be attributed to the development of various transceiver technologies. At the transmitter, LEDs should provide high-quality light for illumination and support wide modulation bandwidths. Meanwhile, at the receiver, optics systems should have functions such as optical filtering, light concentration, and, ideally, a wide field of view (FOV). The photodetector must efficiently convert the optical signal into an electrical signal. Different VLC systems typically consider various transceiver designs. In this paper, we provide a survey of some important emerging technologies used to create advanced optical transceivers in VLC.

Evolution of Hybrid LiFi-WiFi Networks: A Survey.

Given the growing number of devices and their need for internet access, researchers are focusing on integrating various network technologies. Concerning indoor wireless services, a promising approach in this regard is to combine light fidelity (LiFi) and wireless fidelity (WiFi) technologies into a hybrid LiFi and WiFi network (HLWNet). Such a network benefits from LiFi's distinct capability for high-speed data transmission and from the wide radio coverage offered by WiFi technologies. In this paper, we describe the framework for the HWLNet architecture, providing an overview of the handover methods used in HLWNets and presenting the basic architecture of hybrid LiFi/WiFi networks, optimization of cell deployment, relevant modulation schemes, illumination constraints, and backhaul device design. The survey also reviews the performance and recent achievements of HLWNets compared to legacy networks with an emphasis on signal to noise and interference ratio (SINR), spectral and power efficiency, and quality of service (QoS). In addition, user behaviour is discussed, considering interference in a LiFi channel is due to user movement, handover frequency, and load balancing. Furthermore, recent advances in indoor positioning and the security of hybrid networks are presented, and finally, directions of the hybrid network's evolution in the foreseeable future are discussed.

Image-free active autofocusing with dual modulation and its application to Fourier single-pixel imaging.

Autofocusing is widely used in applications where sharp image acquisition or projection is needed. Here we report an active autofocusing method for sharp image projection. The method works with wide-field structured illumination and single-pixel detection. To find the focus position, the method illuminates the target object with a set of 3-step phase-shifting Fourier basis patterns repeatedly and collects the backscattered light by using a single-pixel detector through a grating. Dual modulation-dynamic modulation by the time-varying structured illumination and static modulation by the grating-embeds the depth information for the target object in the resulting single-pixel measurements. As such, the focus position can be determined by recovering the Fourier coefficients from the single-pixel measurements and searching for the coefficient with the maximum magnitude. High-speed spatial light modulation not only enables rapid autofocusing but also makes the method work even when the lens system is in continuous motion or the focal length of the lens is continuously adjusted. We experimentally validate the reported method in a self-built digital projector and demonstrate the application of the method in Fourier single-pixel imaging.

Microsphere-assisted dark-field microscopy based on a fully immersed low refractive index microsphere.

Here we find that a fully immersed low refractive index SiO2 microsphere (or a microcylinder, a yeast cell) can clearly distinguish a sample with sub-diffraction features in dark-field illumination mode. The resolvable area of the sample by microsphere-assisted microscopy (MAM) is composed of two regions. One region locates below the microsphere, and a virtual image of this part of the sample is formed by the microsphere first and then the virtual image is received by the microscope. The other region is around the edge of the microsphere, and this part of the sample is directly imaged by the microscope. The simulated region of the enhanced electric field on the sample surface formed by the microsphere is consistent with the resolvable region in the experiment. Our studies show that the enhanced electric field on the sample surface generated by the fully immersed microsphere plays an important role in dark-field MAM imaging, and this finding will have a positive effect on exploring novel mechanisms in resolution improvement of MAM.

Centimeter-wave Free-space Neural Time-of-Flight Imaging

Depth sensors have emerged as a cornerstone sensor modality with diverse applications in personal hand-held devices, robotics, scientific imaging, autonomous vehicles, and more. In particular, correlation Time-of-Flight (ToF) sensors have found widespread adoption for meter-scale indoor applications such as object tracking and pose estimation. While they offer high depth resolution at competitive costs, the precision of these indirect ToF sensors is fundamentally limited by their modulation contrast, which is in turn limited by the effects of photo-conversion noise. In contrast, optical interferometric methods can leverage short illumination modulation wavelengths to achieve depth precision three orders of magnitude greater than ToF, but typically find their range is restricted to the sub-centimeter. In this work, we merge concepts from both correlation ToF design and interferometric imaging; a step towards bridging the gap between these methods. We propose a computational ToF imaging method that optically computes the GHz ToF correlation signal in free space before photo-conversion. To acquire a depth map, we scan a scene point-wise and computationally unwrap the collected correlation measurements. Specifically, we repurpose electro-optical modulators used in optical communication for ToF imaging with centimeter-wave signals, and achieve all-optical correlation at 7.15 GHz and 14.32 GHz modulation frequencies. While GHz modulation frequencies increase depth precision, these high modulation rates also pose a technical challenge. They result in dozens of wraps per meter which cannot be estimated robustly by existing phase unwrapping methods. We tackle this problem with a proposed segmentation-inspired phase unwrapping network , which exploits the correlation of adjacent GHz phase measurements to classify regions into their respective wrap counts. We validate this method in simulation and experimentally, and demonstrate precise depth sensing using centimeter wave modulation that is robust to surface texture and ambient light. Compared to existing analog demodulation methods, the proposed system outperforms all of them across all tested scenarios. CCS Concepts: • Computing methodologies ;

Optical lattices engineered by vector polarization and multisector amplitude modulation

Optical lattices have several applications including super-resolution imaging, lithography, and light-tweezers. Compared with the conventional multibeam interference method, optical lattices in a tightly focused light fields are presented by cylindrical vector polarization illumination and multisector amplitude modulation. The polarization and phase difference of the illumination beam, including the size and relative position of the sectors, were analyzed using the vector diffraction theory. The obtained results indicate that the primitive cell shape of optical lattices can be controlled by the polarization direction of the illumination beam when the relative positions of sectors in the amplitude modulation mask are set. In addition, the period and primitive cell shape of optical lattices with hyper or complex constructions can be controlled by the relative positions of sectors, while the optical lattice zone primarily depends on the sector size. By combining polarization and amplitude modulation in a high numerical aperture optical system, these engineered optical lattices are potentially beneficial in expanding their applications.

Syntrophy between fermentative and purple phototrophic bacteria to treat and valorize carbohydrate-rich wastewaters

Fermentative chemoorganoheterotrophic bacteria (FCB) and purple photoorganoheterotrophic bacteria (PPB) are two interesting microbial guilds to process carbohydrate-rich wastewaters. Their metabolic interactions have been studied in pure cultures or co-cultures, but little is known about mixed cultures. We studied the effect of reactor regimes (batch/chemostat) and illumination modes (continuous infrared light, dark, or light/dark cycles) on glucose conversions and process ecology of the interactions between FCB and PPB in mixed cultures. In batch, FCB (>80 % of sequencing read counts) outcompeted PPB, under any light conditions. In chemostat under continuous and alternating irradiance, three FCB populations were enriched (>70 %), while Rhodobacteraceae (PPB) made 30 % of the community. Glucose fermentation products were linked to the dominant FCB. Continuous culturing helped maintaining FCB and PPB in syntrophy: PPB grew on glucose metabolites produced by FCB. Engineering the association between FCB and PPB in mixed-culture processes can help to treat and valorize carbohydrate-rich aqueous waste.

Full-field single molecule localization microscopy with a mono-detector.

Fluorescence super-resolution microscopy has reached the ultimate detection limit of individual molecules. The sparsity property has enabled a change of paradigm from a diffraction-limited resolution in the few hundred nanometer range to a molecular localization-based resolution in the few nanometer range. Usually, single molecule localization microscopies are based on PSF fitting using a camera detector. Alternatively, another localization strategy is possible based on the dependence of the fluorophore emission on the illumination. A sequence of acquisition using different structured illuminations can be used to localize the emitter. This excitation-based strategy has been applied successfully for wide-field images using a shifting modulated illumination synchronized with a camera (ModLoc, SIMFlux, ROSE,…) and in a scanning approach configuration (MinFlux) with a single detector. However, these localization techniques are limited by the slowness of the camera in their full-field configuration and by the scanning approach in their mono-detector configuration. In this work, we present a novel concept for molecular localization microscopy where the information of the entire full-field image is given by the emitted photon flux. Although working as a full-field technique, this allows emitter localization via the acquisition of the fluorescence light by a single photon counting module, rather than a camera, which has the immediate advantage of gaining temporal resolution. The theoretical resolution limit (given by its Cramér-Rao lower bounds) gives a better localization precision as compared to the standard PSF fitting. We will show experimental characterization of this new localization technique in terms of spatial precision and temporal performances. Imaging of calibrated samples, as well as cytoskeleton network in COS7 cells will be presented, and the different assets of this new approach will be fully discussed.

Influence of Pulsed, Scanning and Constant (16- and 24-h) Modes of LED Irradiation on the Physiological, Biochemical and Morphometric Parameters of Lettuce Plants (Lactuca sativa L.) while Cultivated in Vertical Farms

In city farming, when growing green crops, a significant part of the production cost is the cost of electricity for lighting. The physiology, biochemistry, morphology and productivity of plants can be affected by changing irradiation modes and these changes reduce electricity costs. However, the results of studies in the literature are contradictory. In this work, we investigated the effect of impulse (frequency 1000 Hz and duty cycle 67%), scanning (the principle of running lights) and constant 16 h and 24 h modes of operation of white light LED irradiators on the physiological, biochemical and morphometric parameters of lettuce with red and green leaves. The daytime integral of light in all variants remained unchanged ~15.6 mol m−2 day−1. Daily electricity consumption also did not differ significantly. Plants were grown on racks in a climatic chamber up to 35 days of age. For lettuce with red leaves, the most optimal for biomass accumulation and synthesis of anthocyanins was the impulse illumination mode, while for lettuce with green leaves, no statistically significant differences in biomass were observed under different irradiation modes. For red-leaved lettuce, it was found that the highest concentration of carotenoids in the leaf was observed under constant (24 h) and scanning irradiation, which is associated with a more active reaction of the photosynthetic system to prolonged irradiation and increased intensity during scanning irradiation. Also, increased photosynthetic activity was found in both varieties of lettuce at 16 h of operation of LED irradiators, which, however, did not affect their final productivity. The results may be useful for the development of LED illuminators for use in rack growing.

Design and Application of Phase-Only Diffractive Optical Element Based on Non-Iterative Method

In this study, we devised a method for the design of continuous phase-only holographic masks that map laser light to arbitrary target illumination patterns, which have a wide range of applications. In this method, the discrete gradient of a holographic mask is obtained by combining geometric optics and the linear assignment problem (LAP) methods, and then the entire problem is transformed into an integral problem with a discrete gradient. Finally, the least squares method is used to solve the gradient integral to complete the construction of a phase holographic mask. Due to its good continuity, this mask design method can also be applied to the production of diffractive optical elements. We discussed the effectiveness of this method by constructing two holographic masks with uniform illumination. At the same time, we successfully constructed an Einstein face holographic mask with non-uniform illumination using the LAP method for the first time. It is believed that this method can be widely used in illumination mode, ion capture and other directions.

Axial resolution and imaging contrast enhancement in inverted light-sheet microscopy by natural illumination modulation.

Inverted light-sheet microscopy (ILSM) is widely employed for fast large-volume imaging of biological tissue. However, the scattering especially in an uncleared sample, and the divergent propagation of the illumination beam lead to a trade-off between axial resolution and imaging depth. Herein, we propose naturally modulated ILSM (NM-ILSM) as a technique to improve axial resolution while simultaneously maintaining the wide field-of-view (FOV), and enhancing imaging contrast via background suppression. Theoretical derivations, simulations, and experimental imaging demonstrate 15% axial resolution increases, and fivefold greater image contrast compared with conventional ILSM. Therefore, NM-ILSM allows convenient imaging quality improvement for uncleared tissue and could extend the biological application scope of ILSM.

Illumination and gaze effects on face evaluation: The Bi-AGI database.

Face evaluation and first impression generation can be affected by multiple face elements such as invariant facial features, gaze direction and environmental context; however, the composite modulation of eye gaze and illumination on faces of different gender and ages has not been previously investigated. We aimed at testing how these different facial and contextual features affect ratings of social attributes. Thus, we created and validated the Bi-AGI Database, a freely available new set of male and female face stimuli varying in age across lifespan from 18 to 87 years, gaze direction and illumination conditions. Judgments on attractiveness, femininity-masculinity, dominance and trustworthiness were collected for each stimulus. Results evidence the interaction of the different variables in modulating social trait attribution, in particular illumination differently affects ratings across age, gaze and gender, with less impact on older adults and greater effect on young faces.

Using optical flow algorithm based on dynamic illumination mode to examine defects on highly reflective turbine blade surface

Notion of optical flow literally refers to the displacements of intensity patterns. In that sense, extracting interested information from 2D scene is analogy to modulation/demodulation in random signal processing. To address the limitations presented in computer vision based on static image, we propose a novel metal component defect detection method, specified as the instance of turbine blade surface detection, using optical flow estimation.To start the specified pattern recognition in 2D presentation, we modulate the brightness constancy assumption equation as illumination varying model, by sampling the second image with function whose frequency was chosen according to the Nyquist sampling theorem, and a sinusoidal factor was introduced as an additive factor. This tunable channel based on 2D image transfers intensity features into optical modes. Then, we implement optical flow estimation on two sequential images. Experimental results reveal grayscale space shows completness in representing the optical modes of turbine blade with various kinds of surface characteristics. By modifying the index of information content, we propose quantitative index to evaluate the performance of our method. Evaluation reveals optical flow algorithm is qualified to examine defects on highly reflective turbine blade, and our method extends the application of optical flow.

Camera-Derived Photoplethysmography (rPPG) and Speckle Plethysmography (rSPG): Comparing Reflective and Transmissive Mode at Various Integration Times Using LEDs and Lasers.

Background: Although both speckle plethysmography (SPG) and photoplethysmography (PPG) examine pulsatile changes in the vasculature using opto-electronics, PPG has a long history, whereas SPG is relatively new and less explored. The aim of this study was to compare the effects of integration time and light-source coherence on signal quality and waveform morphology for reflective and transmissive rSPG and rPPG. Methods: (A) Using time-domain multiplexing, we illuminated 10 human index fingers with pulsed lasers versus LEDs (both at 639 and 850 nm), in transmissive versus reflective mode. A synchronized camera (Basler acA2000-340 km, 25 cm distance, 200 fps) captured and demultiplexed four video channels (50 fps/channel) in four stages defined by illumination mode. From all video channels, we derived rPPG and rSPG, and applied a signal quality index (SQI, scale: Good > 0.95; Medium 0.95–0.85; Low 0.85–0.8; Negligible < 0.8); (B) For transmission videos only, we additionally calculated the intensity threshold area (ITA), as the area of the imaging exceeding a certain intensity value and used linear regression analysis to understand unexpected similarities between rPPG and rSPG. Results: All mean SQI-values. Reflective mode: Laser-rSPG > 0.965, LED-rSPG < 0.78, rPPG < 0.845. Transmissive mode: 0.853–0.989 for rSPG and rPPG at all illumination settings. Coherent mode: Reflective rSPG > 0.951, reflective rPPG < 0.740, transmissive rSPG and rPPG 0.990–0.898. Incoherent mode: Reflective all <0.798 and transmissive all 0.92–0.987. Linear regressions revealed similar R2 values of rPPG with rSPG (R2 = 0.99) and ITA (R2 = 0.98); Discussion: Laser-rSPG and LED-rPPG produced different waveforms in reflection, but not in transmission. We created the concept of ITA to investigate this behavior. Conclusions: Reflective Laser-SPG truly originated from coherence. Transmissive Laser-rSPG showed a loss of speckles, accompanied by waveform changes towards rPPG. Diffuse spatial intensity modulation polluted spatial-mode SPG.

Detection of early decayed oranges by structured-illumination reflectance imaging coupling with texture feature classification models.

Citrus fruits are susceptible to fungal infection after harvest. To reduce the economic loss, it is necessary to reject the infected citrus fruit before storage and transportation. However, the infected area in the early stage of decay is almost invisible on the fruit surface, so the detection of early decayed citrus is very challenging. In this study, a structured-illumination reflectance imaging (SIRI) system combined with a visible light-emitting diode (LED) lamp and a monochrome camera was developed to detect early fungal infection in oranges. Under sinusoidal modulation illumination with spatial frequencies of 0.05, 0.15, and 0.25 cycles mm–1, three-phase-shifted images with phase offsets of − 2π/3, 0, and 2π/3 were acquired for each spatial frequency. The direct component (DC) and alternating component (AC) images were then recovered by image demodulation using a three-phase-shifting approach. Compared with the DC image, the decayed area can be clearly identified in the AC image and RT image (AC/DC). The optimal spatial frequency was determined by analyzing the AC image and pixel intensity distribution. Based on the texture features extracted from DC, AC, and RT images, four kinds of classification models including partial least square discriminant analysis (PLS-DA), support vector machine (SVM), least squares-support vector machine (LS-SVM), and k-nearest neighbor (KNN) were established to detect the infected oranges, respectively. Model optimization was also performed by extracting important texture features. Compared to all models, the PLS-DA model developed based on eight texture features of RT images achieved the optimal classification accuracy of 96.4%. This study showed for the first time that the proposed SIRI system combined with appropriate texture features and classification model can realize the early detection of decayed oranges.

High‐Speed All‐Fiber Micro‐Imaging with Large Depth of Field

AbstractSingle fiber imaging has evolved into a powerful method for detecting minute objects in narrow spaces. However, existing systems are not conducive to imaging dynamic objects at depth due to their bulky probes, time‐consuming scanning acquisition methods, and transmissive illumination mode. Minimally invasive reflection mode imaging with high spatial and temporal resolution remains an open challenge. Here, a precise and high‐speed imaging scheme without scanning is proposed. Multimode fiber imaging technology is incorporated into an all‐fiber aberration‐free precision detection system. High temporal resolution (5000 fps) detection of tiny natural scenes is experimentally realized by optimizing the approximation of the inverse transmission matrix in a simple and compact setup. The system can display the detected screen in real‐time and the computational imaging with a large depth of field (1 mm) is enabled by jointly learning. The recovery results are superior compared to typical deep neural networks. The demonstrated scheme offers a new possibility for many applications, for example, microendoscopy, all‐optical computing, and remote high‐speed video transmission.

Super-resolution optical microscopy using cylindrical vector beams

AbstractSuper-resolution optical microscopy, which gives access to finer details of objects, is highly desired for fields of nanomaterial, nanobiology, nanophotonics, etc. Many efforts, including tip optimization and illumination optimization etc., have been made in both near-field and far-field super-resolution microscopy to achieve a spatial resolution beyond the diffraction limit. The development of vector light fields opens up a new avenue for super-resolution optical microscopy via special illumination modes. Cylindrical vector beam (CVB) has been verified to enable resolution improvement in tip-scanning imaging, nonlinear imaging, stimulated emission depletion (STED) microscopy, subtraction imaging, superoscillation imaging, etc. This paper reviews recent advances in CVB-based super-resolution imaging. We start with an introduction of the fundamentals and properties of CVB. Next, strategies for CVB based super-resolution imaging are discussed, which are mainly implemented by tight focusing, depletion effect, plasmonic nanofocusing, and polarization matching. Then, the roadmap of super-resolution imaging with CVB illumination in the past two decades is summarized. The typical CVB-based imaging techniques in fields of both near-field and far-field microscopy are introduced, including tip-scanning imaging, nonlinear imaging, STED, subtraction imaging, and superoscillation imaging. Finally, challenges and future directions of CVB-illuminated super-resolution imaging techniques are discussed.