Light Intensity Distribution Research Articles

Deep Mutual Learning-Based Mode Recognition of Orbital Angular Momentum

Due to its orbital angular momentum (OAM), optical vortex has been widely used in communications and LIDAR target detection. The OAM mode recognition based on deep learning is mostly based on the basic convolutional neural network. To ensure high-precision OAM state detection, a deeper network structure is required to overcome the problem of similar light intensity distribution of different superimposed vortex beams and the effect of atmospheric turbulence disturbance. However, the large number of parameters and the computation of the OAM state detection network conflict with the requirements of deploying optical communication system equipment. In this paper, an online knowledge distillation scheme is selected to achieve an end-to-end single-stage training and the inter-class dark knowledge of similar modes are fully utilized. An optical vortex OAM state detection technique based on deep mutual learning (DML) is proposed. The simulation results show that after mutual learning training, a small detection network with higher accuracy can be obtained, which is more suitable for terminal deployment. Based on the scalability of the number of networks in the DML queue, it provides a new possibility to further improve the detection accuracy of the optical communication.

Broad-wave reflection of polymer-stabilised cholesterol liquid crystal with nanofibers doped magnetic nanoparticles

ABSTRACT In this study, the polymer-stabilised cholesterol-based liquid crystal (PSCLC) films with broad-wave reflection were prepared via PVA nanofibers as carriers loaded with Fe3O4 nanoparticles. Fe3O4 nanoparticles have absorption properties in the UV region. When UV light is irradiated along the thickness of the liquid crystal cell, the resulting gradient distribution of UV light intensity induces a gradient distribution of spacing and thus a broad-wave reflection. Specifically, the effects of nanoparticles content loaded in nanofibers, magnetic field strength, polymerisation time and temperature, UV light intensity and polymerised monomer content were studied. The result shows that the proper contents of Fe3O4 nanoparticles and the polymerisation conditions have favourable impacts on the broad-wave reflection of PSCLC films. To clarify the mechanism of formed broad-wave reflection, the morphology of nanofibers was observed by scanning electron microscopy (SEM). The modification of nanoparticles was collected by transmission electron microscopy (TEM) and infrared spectroscopy. The texture of PSCLC films was observed by POM. The broad-wave reflection were measured by UV-Vis spectrophotometer. This strategy broadens the broad-wave reflection of PSCLC films from 300 nm to 476 nm increasing its application potential in UV shielding devices, and infrared thermal control devices.

A Monoblock Light-Scattering Milk Fat Percentage and Somatic Cell Count Sensor for Use in Milking Systems.

A monoblock light-scattering sensor, which is capable of measuring the fat content of milk and indicating the excess by which the somatic cell count (SCC) is over the permissible level, has been developed for installation in dairy systems. In order for the sensor to perform measurements when the milking machine is working in the "milk plug" mode, a flow-through unit is designed in the form of a pipe with a lateral cylindrical branch, in which milk accumulates so as to eliminate large bubbles and achieve continuity of the milk flow. The operation of the sensor is based on the registration of the angular intensity distribution of light scattered in the transparent cylindrical segment of the tube branch. A semiconductor laser with a wavelength of 650 nm is used as a light source for determining scattering in milk. The angular distribution of the scattered light intensity (scattering indicatrix) is recorded using an axial photodiode array. The fat content is determined by the average slope of the measured scattering indicatrix in the range of scattering angles 72-162°. The SCC level is estimated from the relative deviation of the forward scatter intensity normalized to the backscatter intensity with respect to uninfected milk. The sensor has been tested on a Yolochka-type milking machine.

Laser stripe center extraction method base on Hessian matrix improved by stripe width precise calculation

The line laser measurement technology based on triangulation is widely used in the field of complex surface topography measurement. The key technology of line laser measurement is laser stripe center extraction. For high reflective surfaces, due to the low surface roughness, some areas of the laser stripe image are overexposed, resulting in uneven stripe width distribution, asymmetric light intensity distribution of the stripe cross section, and difficulty in extracting the center of the stripe. In this paper, Laser stripe center extraction method based on Hessian matrix method improved by stripe width is proposed. Firstly, the laser stripe image is preprocessed, the influence of noise in the image is alleviated by image filtering and adaptive threshold segmentation, and the region of interest of the image is extracted to reduce the amount of subsequent calculation. The laser stripe width is calculated based on BPNN and divided into different width intervals. The Gaussian kernel is calculated according to the light stripe width and the Hessian matrix is constructed. The Hessian matrix method is used to roughly extract the center coordinates of the light stripe. Based on the continuity of the light stripe, the center coordinates of the light stripe are weighted and corrected to realize the smooth optimization of the center coordinates of the light stripe. The experimental results show that the proposed light stripe center extraction method is superior to the traditional method under different surface roughness and exposure time conditions, which can effectively improve the measurement accuracy of the sensor.

Visual similarity simulation of slub denim based on image processing

The slub denim has various appearance styles that attract consumers due to the irregular distribution and long cycle of the slubs in the slub yarn. This characteristic of the slub yarn makes the slub denim proofing that relies on artificial visual contrast time-consuming with a long design cycle. A visual similarity simulation method was proposed for slub denim based on slub yarn images to solve this problem. At first, the yarn images were pre-processed by grey-level transformation, image threshold segmentation, and morphological operations to obtain the yarn core images. Secondly, according to the elastic change of yarn in fabric structure, the elliptic and sine curve models were established to treat the string to obtain the actual yarn shape in the fabric. Then, a light intensity curve function, which consists of a radial curve model and an interlacing point curve model, was established to simulate the light intensity distribution on the yarn surface. Finally, the cover relation of warp and weft yarns was controlled by Boolean matrix, and mean filtering was used to adjust the fuzzy denim fabric images. The experimental results show that the slub denims simulated by the method proposed in this article have a high visual similarity with the actual slub denims. Meanwhile, multiple parameters of the simulation model established in this article can be adjusted to enhance the adaptability of the model and the accuracy of the simulation results.

Design study of a micro illumination platform based on GaN microLED arrays.

The design study of a micro illumination tool based on GaN microLED arrays is presented. The high spatio-temporal resolution and the capability of generating fully customized optical patterns that characterize the proposed platform would enable the manipulation of biological systems, e.g.,for optogenetics applications. Based on ray tracing simulations, the design aspects that mainly affect the device performance have been identified, and the related structural parameters have been optimized to improve the extraction efficiency and the spatial resolution of the resulting light patterns. Assuming that the device is a bottom emitter, and the light is extracted from the n-side, the presence of mesa-structures on the p-side of the GaN layer can affect both the efficiency and the resolution, being optimized for different values of the mesa-side inclination angle. The full width at half maximum (FWHM) of the extracted spots is mainly determined by the substrate thickness, and the relation between the FWHM and the array pitch represents a criterion to define the resolution. Namely, when F W H M<p i t c h, the spots are assumed to be resolved, while, when F W H M=p i t c h, a homogeneous distribution of light intensity is observed. The best performance is obtained when an in-GaN micro-lens array is included in the simulated structure, assuming that the substrate has been removed. The spatial resolution of the generated light pattern results as fully preserved, while the extraction efficiency in the best case is up to three times larger than that of a planar GaN/air interface.

Transmission Characteristics and Spatial Coherence of Partially Coherent Light-Emitting Diode Array in the Ocean

Underwater LED light sources are commonly implemented in array configurations with a wide-angle field of view, primarily catering to high-speed communication within a few meters. To increase transmission distance and mitigate oceanic turbulence effects, this paper focuses on the spatial coherence analysis of narrow-beam partially coherent light-emitting diode (PCLED) arrays, examining their average light intensity distribution, beam width, and spatial coherence during oceanic transmission. Based on the extended Huygens–Fresnel integral, the optical field models and spatial characteristics of the radial PCLED array are derived under oceanic conditions, considering parameters such as water attenuation coefficient, kinetic energy dissipation rate, temperature dissipation rate, temperature-to-salinity ratio, as well as the radial filling factor and the sub-beam spatial coherence length of the light source at different transmission distances. The simulations show that, as the spatial coherence length of the sub-beam decreases from hundreds to a few micrometers, the combining distance of the beam arrays also decreases. This reduction in coherence results in the average light intensity distribution degrading into a Gaussian-like distribution, with a significant five-fold decrease in peak intensity. Furthermore, the width of the array spreads, starting from distances of 7 m and 0 m, respectively. The radial PCLED beam array, with its sub-beam spatial coherence length inside micrometers, possesses inherent characteristics that suppress turbulence effects and has future extensive possibilities in the ocean.

Improvement in Signal Phase Detection Using Deep Learning with Parallel Fully Connected Layers

We report a single-shot phase-detection method using deep learning in a holographic data-storage system. The error rate was experimentally confirmed to be reduced by up to three orders of magnitude compared with that in the conventional phase-determination algorithm by learning the light-intensity distribution around a target signal pixel. In addition, the output speed of a signal phase could be shortened by devising a network and arranging the fully connected layers in parallel. In our environment, the phase-output time of a single-pixel classification was approximately 18 times longer than that in our previous method, with the minimum-finding algorithm. However, it could be reduced to 1.7 times or less when 32 pixels were simultaneously classified. Therefore, the proposed method can significantly reduce the error rates and suppress the phase-output time to almost the same level as that in the previous method. Thus, our proposed method can be a promising phase-detection method for realizing a large-density data-storage system.

Classroom Energy-saving Control System Design

With the continuous development of science and technology, the degree of automation of various products in life is increasing. However, the impact on energy consumption and environment is getting bigger and bigger, and energy saving and emission reduction is gradually becoming a hot topic in the society. The huge loss of electrical energy in colleges and universities makes the development of energy-saving control technology particularly important. In this paper, we design an energy-saving control system for college classrooms based on STM32 main controller, which mainly collects the light intensity and personnel distribution information of classrooms through photoresistor sensors and infrared pyroelectric sensors, and combines software programming to realize effective and group control of classroom lights, so as to achieve the purpose of energy saving. On this basis, a simple upper computer monitoring interface is built to display the collected information, which facilitates real-time monitoring and management of the classroom. The system is analyzed and introduced in detail in three main aspects in the paper. Firstly, the selection of the main controller and its main hardware circuit modules are introduced; secondly, the software process design is centered around the system; finally, using simulation, analysis and online debugging, the light intensity and personnel distribution information collected can be used to control the lamps and lanterns at the corresponding locations of the personnel to turn on. In summary, this paper designs a classroom energy-saving control system to meet the current situation of large energy consumption in college classrooms, which can realize the effective lighting of the corresponding positions according to the changes of natural light environment and different positions of the personnel in the classroom, and verifies the feasibility of this scheme. It provides an idea to effectively reduce the waste of power resources and achieve the purpose of energy saving and emission reduction in colleges and universities.

Segmented modelling and analysis of disperse dye concentration based on multidimensional spectrum

AbstractSince the water‐insoluble dispersing dye has both absorption and scattering characteristics, a spatial resolution hyperspectral measurement approach and experimental testing was proposed in this article, which can collect spectral and spatial data from samples simultaneously. The concentration of 81 groups of three‐component disperse dye samples were measured. However, the hyperspectral data of dye solutions in the 420–800 nm band is saturated, resulting in the inability for multispectral data processing. A segmented concentration quantitative analysis model was developed. For the unsaturated band (420–510 nm), the partial least squares (PLS), the N‐way partial least squares (NPLS), and support vector machine (SVM) models using the data points on the X‐axis of a two‐dimensional light intensity distribution map were established. The predicted performance of PLS model was worse slightly than that of the other two models, The coefficient of determination (R2) values of concentrations for red, orange and blue disperse dye were 0.888, 0.796 and 0.959, respectively. For saturated band (520–670 nm), the NPLS and SVM models using the data points on the X‐ and Y‐axis were established. Results shows that the prediction accuracy of concentrations of the three‐component disperse dye was increased by adding additional data points on the Y‐axis, with R2 values of 0.944, 0.807, and 0.912, respectively. For the strong scattering band (680–800 nm), a SVM model was established, and R2 of concentration of the three dyes reached 0.974, 0.933 and 0.995, respectively. The results showed that multidimensional spectroscopy method can improve the prediction accuracy of component concentration of disperse dye solution, by using more spectral information from X and Y directions.

Inner-cavity generation of mid-infrared optical vortex arrays from an Er:CaF2 laser

We demonstrate the inner-cavity generation of mid-infrared optical vortex arrays from an Er:CaF2 laser. By shifting the position of the defect point on the input mirror, multiple transverse modes simultaneously oscillated in the cavity and constituted vortex arrays by transverse mode locking. The maximum output power of TEM00 mode could reach 440 mW with a low threshold of 463 mW. The maximum output powers of LG0,1, the 1 × 2 and the 2 × 2 vortex arrays were 254 mW, 131 mW, and 117 mW, respectively. The chirality of the vortex arrays could be reversed by slightly adjusting the geometric loss of the cavity. The light intensity distribution, interference, and phase distribution were simulated and they were in good accordance with the experimental results. This method provides deep insight into inner-cavity generation of vortex arrays in mid-infrared regime.

Intensity Ratio Distribution in Different Dielectric Liquids using Kerr Effect Method

Light intensity is the result from the Kerr effect measurement that can be used in determining the electric field distributions in dielectric liquids as the analysis continues afterwards. One of the most important parameters to consider in designing the Kerr effect experiment is the Kerr constant of the test liquid. This paper aims to study and compare light intensity distribution in different dielectric liquids using Kerr effect method. Propylene carbonate, transformer oil and purified water are used as the test liquids. From the results obtained, the light intensities as a function of electric field of the test liquids are compared. With higher Kerr constant, low voltages can be applied to the test liquid but with larger optical signals. Furthermore, the length of the electrodes can be designed accordingly to suit the experimental setup.

Optimal analysis of optical parameters of road tunnel opening scrimshaw

With the development of technology, more and more cities and highways are installing light reducing structures at the tunnel openings to improve traffic safety and reduce the “black hole effect” and low-angle sunlight glare effect. However, the existing scrims have poor road surface uniformity, bright and dark streaks and uneven road surface brightness, which can bring negative impact on driving. In order to balance the safety and comfort of tunnel light sheds, a new technique is proposed to reduce the negative effects of light sheds based on the multi-source effect of light diffusion panels. The results show that by arranging light diffusion panels on the top of the scrim, the daylight is fully diffused and then irradiated to the road surface under the scrim, avoiding the undesirable phenomenon caused by direct sunlight on the road surface. After the indoor test and numerical model analysis, the effectiveness of the technology is proved to be in compliance with the design specification, and the undesirable phenomena such as bright and dark streaks are avoided, thus ensuring the safety and comfort of traffic at the tunnel entrance. In addition, the average brightness of the road surface of the top arrangement of light diffusion panels is better than that of the two sides, and the light intensity distribution curve of No. 2 panel among the four light diffusion panels used in this paper is the best. The technology can also control the brightness level of the road surface under the shed through the area of light diffusion panels, thus reducing the carbon emission of the tunnel lighting system and achieving the unity of safety, comfort and low carbon environment protection.

Mapping optical scattering properties to physical particle information in singly and multiply scattering samples.

Optical coherence tomography (OCT) leverages light scattering by biological tissues as endogenous contrast to form structural images. Light scattering behavior is dictated by the optical properties of the tissue, which depend on microstructural details at the cellular or sub-cellular level. Methods to measure these properties from OCT intensity data have been explored in the context of a number of biomedical applications seeking to access this sub-resolution tissue microstructure and thereby increase the diagnostic impact of OCT. Most commonly, the optical attenuation coefficient, an analogue of the scattering coefficient, has been used as a surrogate metric linking OCT intensity to subcellular particle characteristics. To record attenuation coefficient data that is accurately representative of the underlying physical properties of a given sample, it is necessary to account for the impact of the OCT imaging system itself on the distribution of light intensity in the sample, including the numerical aperture (NA) of the system and the location of the focal plane with respect to the sample surface, as well as the potential contribution of multiple scattering to the reconstructed intensity signal. Although these considerations complicate attenuation coefficient measurement and interpretation, a suitably calibrated system may potentiate a powerful strategy for gaining additional information about the scattering behavior and microstructure of samples. In this work, we experimentally show that altering the OCT system geometry minimally impacts measured attenuation coefficients in samples presumed to be singly scattering, but changes these measurements in more highly scattering samples. Using both depth-resolved attenuation coefficient data and layer-resolved backscattering coefficients, we demonstrate the retrieval of scattering particle diameter and concentration in tissue-mimicking phantoms, and the impact of presumed multiple scattering on these calculations. We further extend our approach to characterize a murine brain tissue sample and highlight a tumor-bearing region based on increased scattering particle density. Through these methods, we not only enhance conventional OCT attenuation coefficient analysis by decoupling the independent effects of particle size and concentration, but also discriminate areas of strong multiple scattering through minor changes to system topology to provide a framework for assessing the accuracy of these measurements.

Investigating pulsed LED effectiveness as an alternative to continuous LED through morpho-physiological evaluation of baby leaf lettuce (Lactuca sativa L. var. Acephala)

Photoperiod, light intensity, and spectral quantum distribution (SPD) affect plant development and physiology. Light determines morphological signals, influences plant behavior and regulates metabolism in addition to providing energy for photosynthesis. In this experiment, lettuce (Lactuca sativa) was grown in an indoor LED-equipped chamber, operated in a pulsed and continuous mode, with an average photosynthetic photon flux density (PPFD) at a seedling level of 150 µmole s¯¹ m¯², photoperiod of 16 h for growing cycle of 30 days. The primary aim of this study was to observe the effects of varying LED on the growth and quality of the produce. Regardless of the treatments, in both continuous and pulsed LED, an increment in the yield, leaf length and leaf width of lettuce was recorded in comparison to the control, which was managed in a glasshouse under controlled environmental conditions using a winter cropping cycle. In-vitro physiological analysis of lettuce revealed the outperformance of the continuous LED treatment over the pulsed LED as well as the control in terms of total sugars, chlorophyll concentration, carotenoids, phenolic index, and sucrose accumulation. Continuous LED treatment has also resulted in a significant reduction in nitrate content, a commercially vital parameter, making it the most advantageous and effective of all the treatments performed. However, the production of anthocyanins, an antioxidant released during stress, was enhanced under pulsed LED which requires further investigation and improvements to achieve an improved metabolite profile of lettuce with a minimal energy usage and cost.

Angle-Dependent Transport Theory-Based Ray Transfer Function for Non-Contact Diffuse Optical Tomographic Imaging

This work presents a generalized angle-dependent ray transfer function that can accurately map the angular and spatial distribution of light intensities on the tissue surface onto a camera image plane in a non-contact camera-based imaging system. The method developed here goes beyond existing ray transfer models that apply to angle-averaged tomographic data alone. The angle-dependent ray transfer operator was constructed using backward ray tracing based on radiation surface theory. The proposed method was validated using numerical phantoms and experimental data from an actual non-contact imaging system.

Three-dimensional modelling of blur property for conventional optical microscopes

Intensity diffusion caused by optical diffraction limits the imaging resolution of conventional optical microscopes, therefore modelling and measuring the intensity transmission and distribution property of the light sources is a significant research topic in system development and pattern recognition. However, the complicated wave propagation process in optical imaging makes it difficult to provide a direct, analytical and simple mathematical model to measure the relationship between the blur degree and various camera parameters. In this study, an improved intensity transmission and distribution calculation method for conventional optical microscopes was proposed; furthermore, a simple mathematical relation between the blur degree and camera parameters was achieved based on the proposed method. First, the light intensity distribution and propagation characteristics of a conventional optical microscope were modeled based on the property of the Fresnel circular hole diffraction combined with the practical optical parameters. Second, by analyzing the property of intensity distribution and blurring imaging, a quantitative simplified mathematical relationship between the blur degree and camera parameters in optical microscope imaging was obtained, and the three-dimensional (3D) blur property in the optical imaging process was analyzed under different conditions. Third, the connection between diffractive optics and geometric optics was obtained by summarizing and generalizing the 3D blur property curve of each monochromatic light source. Finally, the proposed method was verified through a series of simulations and experiments.

Outdoor Lighting Promoting Well-Being

It is becoming widely understood that besides affecting visual, social and psychological environment, outdoor lighting is also biological environment. This review combines lighting related research efforts of various fields and provides insights for outdoor lighting supporting well-being. The review focuses on the well-being of humans but it is acknowledged that the well-being of humans is largely based on the well-being of the whole ecosystem. The review also briefly discusses the effects of artificial light at night on various organisms and biological systems. Finally, the review summarizes the research results on the possible effects on well-being caused by the changes in intensity, spectrum, spatial distribution and temporal distribution of light. The focus is on the mesopic lighting conditions, as the outdoor environments typically represent such light levels. The results are targeted to affect the design choices of outdoor lighting practices.

Experimental Generation of Structured Light Beams through Highly Anisotropic Scattering Media with an Intensity Transmission Matrix Measurement

Structured light beams have played important roles in the fields of optical imaging and optical manipulation. However, light fields scatter when they encounter highly anisotropic scattering media, such as biological tissue, which destroys their original structured fields and turns them into speckle fields. To reconstruct structured light beams through highly anisotropic scattering media, we present a method based on intensity transmission matrix which only relates the input and output light intensity distributions. Compared with the conventional method which relies on the measurement of complex-valued transmission matrix, our scheme is easy to implement, fast and stable. With the assistance of spatial filters, three kinds of structured light beams, Bessel-like beams, vortex beams and cylindrical vector beams, were constructed experimentally through a ZnO scattering layer. The present method is expected to promote optical applications through highly anisotropic scattering media.

Propagating beams carrying orbital angular momentum through simulated optical turbulence generated by Rayleigh–Bénard natural convection

Numerical simulations of Rayleigh–Bénard (RB) convective flow are performed to determine the optical and mechanical turbulence properties and resulting index of refraction field in order to study the propagation characteristics of a laser beam carrying orbital angular momentum. The simulations are carried out in air using a computational fluid dynamics package which solves the Navier-Stokes equations. The computational domain is 0.1 m × 0.5 m × 0.5 m with a temperature difference of 1°K maintained between the top and bottom plate. The simulated temperature field is then converted into refractive index values. To study light propagation through the turbulent volume the split-step screen method is employed with screens at 0.025 m distance from each other along the propagation path which ranges from 0.5 m to 2.5 m. The structure of the phase screens, their spatio-temporal correlation with respect to up/down drafts, and phase changes across regions of interest are discussed. It was observed as the propagation distance increased, the orbital angular momentum carrying Laguerre–Gaussian beams wandered and the beam phase singularity distorted thus impacting the light intensity distribution. In addition, it was found that higher topological charge and order of Laguerre polynomial result in increased distortion of the beam vortex.