Linear Light Source Research Articles

Miniaturized spectroscopy system based on a semiconductor nanofilm

Abstract Spectroscopy plays a pivotal role in various applications for industrial and commercial analysis. Conventional spectroscopy instruments include various discrete optical components like light sources, monochromators and detectors. These components are mechanically intricate and require space for the mechanisms that adjust and calibrate them, which increases the instrument’s footprint and make them less adjustable for portable applications. This drawback initiated the increase in the demand for miniatured spectral detection systems. Here, we present a low-cost ultra-compact miniaturized spectral detection system, which integrates both linear variable light sources, sample chambers and detectors within a centimetre-scale chip. The linear variable light generation across wavelengths ranging from 480 nm to 600 nm is achieved by stimulating different regions of the ZnCdSeS bandgap-graded semiconductor nanofilm with ultraviolet light. We demonstrate the capability of the system with precise identification of liquids. Our device overcomes the typical miniaturization limits imposed by discrete optical components, and long light paths in conventional spectroscopy instruments and opens up numerous potential applications across various fields due to its portability, ease of use, and lower cost.

A Binocular Color Line-Scanning Stereo Vision System for Heavy Rail Surface Detection and Correction Method of Motion Distortion.

Thanks to the line-scanning camera, the measurement method based on line-scanning stereo vision has high optical accuracy, data transmission efficiency, and a wide field of vision. It is more suitable for continuous operation and high-speed transmission of industrial product detection sites. However, the one-dimensional imaging characteristics of the line-scanning camera cause motion distortion during image data acquisition, which directly affects the accuracy of detection. Effectively reducing the influence of motion distortion is the primary problem to ensure detection accuracy. To obtain the two-dimensional color image and three-dimensional contour data of the heavy rail surface at the same time, a binocular color line-scanning stereo vision system is designed to collect the heavy rail surface data combined with the bright field illumination of the symmetrical linear light source. Aiming at the image motion distortion caused by system installation error and collaborative acquisition frame rate mismatch, this paper uses the checkerboard target and two-step cubature Kalman filter algorithm to solve the nonlinear parameters in the motion distortion model, estimate the real motion, and correct the image information. The experiments show that the accuracy of the data contained in the image is improved by 57.3% after correction.

Absolute Photoelectric Encoder Based on Position-Sensitive Detector Sensor

In response to the engineering, miniaturization, and high measurement accuracy requirements of encoders, this paper proposes a new type of absolute photoelectric encoder based on a position-sensitive detector (PSD). It breaks the traditional encoder’s code track design and adopts a continuous and transparent code track design, which has the advantages of small volume, high angle measurement accuracy, and easy engineering. The research content of this article mainly includes the design of a new code disk, decoding circuit, linear light source, and calibration method. The experimental results show that the encoder designed in this article has achieved miniaturization, simple installation and adjustment, and easy engineering. The volume of the encoder is Φ50 mm × 30 mm; after calibration, the resolution is better than 18 bits, and the accuracy reaches 5.4″, which further demonstrates the feasibility of the encoder’s encoding and decoding scheme.

Stacking architecture for collimated backlight using cylindrical lens sheet with linear light sources or edge-lit/direct-lit BLU.

Highly collimated and directional backlights are essential for realizing advanced display technologies such as autostereoscopic 3D displays. Previously reported collimated backlights, either edge-lit or direct-lit, in general still suffer unsatisfactory form factors, directivity, uniformity, or crosstalk etc. In this work, we report a simple stacking architecture for the highly collimated and uniform backlights, by combining linear light source arrays and carefully designed cylindrical lens arrays. Experiments were conducted to validate the design and simulation, using the conventional edge-lit backlight or the direct-lit mini-LED (mLED) arrays as light sources, the NiFe (stainless steel) barrier sheets, and cylindrical lens arrays fabricated by molding. Highly collimated backlights with small angular divergence of ±1.45°∼±2.61°, decent uniformity of 93-96%, and minimal larger-angle sidelobes in emission patterns were achieved with controlled divergence of the light source and optimization of lens designs. The architecture reported here provides a convenient way to convert available backlight sources into a highly collimated backlight, and the use of optically reflective barrier also helps recycle light energy and enhance the luminance. The results of this work are believed to provide a facile approach for display technologies requiring highly collimated backlights.

Correcting the Non-Linear Response of Silicon Photomultipliers.

The finite number of pixels in a silicon photomultiplier (SiPM) limits its dynamic range to light pulses up to typically 80% of the total number of pixels in a device. Correcting the non-linear response is essential to extend the SiPM's dynamic range. One challenge in determining the non-linear response correction is providing a reference linear light source. Instead, the single-step method used to calibrate PMTs is applied, based on the difference in responses to two light sources. With this method, the response of an HPK SiPM (S14160-1315PS) is corrected to linearity within 5% while extending the linear dynamic range by a factor larger than ten. The study shows that the response function does not vary by more than 5% for a variation in the operating voltage between 2 and 5 V overvoltage in the gate length between 20 and 100 ns and for a time delay between the primary and secondary light of up to 40 ns.

Surface Defect Detection of Preform Based on Improved YOLOv5

This paper proposes a lightweight detection model based on machine vision, YOLOv5-GC, to improve the efficiency and accuracy of detecting and classifying surface defects in preforming materials. During this process, clear images of the entire surface are difficult to obtain due to the stickiness, high reflectivity, and black resin of the thermosetting plain woven prepreg. To address this challenge, we built a machine vision platform equipped with a linescan camera and high-intensity linear light source that captures surface images of the material during the preforming process. To solve the problem of defect detection in the case of extremely small and imbalanced samples, we adopt a transfer learning approach based on the YOLOv5 neural network for defect recognition and introduce a coordinate attention and Ghost Bottleneck module to improve recognition accuracy and speed. Experimental results demonstrate that the proposed approach achieves rapid and high-precision identification of surface defects in preforming materials, outperforming other state-of-the-art methods. This work provides a promising solution for surface defect detection in preforming materials, contributing to the improvement of composite material quality.

Design of solar concentrated uniform linear light source of composite ellipsoid cavity

The predecessor of China Optics was China Optics and Applied Optics Digest, which was founded in 1985. At that time, it was the only retrieval journal in the field of optics in China. At the end of 2008, China Optics and Applied Optics Digest was renamed

Electrically stimulated droplet injector for reduced sample consumption in serial crystallography

With advances in X-ray free-electron lasers (XFELs), serial femtosecond crystallography (SFX) has enabled the static and dynamic structure determination for challenging proteins such as membrane protein complexes. In SFX with XFELs, the crystals are typically destroyed after interacting with a single XFEL pulse. Therefore, thousands of new crystals must be sequentially introduced into the X-ray beam to collect full data sets. Because of the serial nature of any SFX experiment, up to 99% of the sample delivered to the X-ray beam during its “off-time” between X-ray pulses is wasted due to the intrinsic pulsed nature of all current XFELs. To solve this major problem of large and often limiting sample consumption, we report on improvements of a revolutionary sample-saving method that is compatible with all current XFELs. We previously reported 3D-printed injection devices coupled with gas dynamic virtual nozzles (GDVNs) capable of generating samples containing droplets segmented by an immiscible oil phase for jetting crystal-laden droplets into the path of an XFEL. Here, we have further improved the device design by including metal electrodes inducing electrowetting effects for improved control over droplet generation frequency to stimulate the droplet release to matching the XFEL repetition rate by employing an electrical feedback mechanism. We report the improvements in this electrically triggered segmented flow approach for sample conservation in comparison with a continuous GDVN injection using the microcrystals of lysozyme and 3-deoxy-D-manno-octulosonate 8-phosphate synthase and report the segmented flow approach for sample injection applied at the Macromolecular Femtosecond Crystallography instrument at the Linear Coherent Light Source for the first time.

Descattering for transmissive inspection in production line using slanted linear image sensors.

We propose a descattering method that can be easily applied to food production lines. The system consists of several sets of linear image sensors and linear light sources slanted at different angles. The images captured by these sensors are partially clear along the direction perpendicular to the sensors. We computationally integrate these images on the frequency domain into a single clear image. The effectiveness of the proposed method is assessed by simulation and real-world experiments. The results show that our method recovers clear images. We demonstrate the applicability of the proposed method to a real production line by a prototype system.

Full‐Stokes imaging polarimetry via random retarder rotation

We report and demonstrate full-Stokes imaging polarimetry via random retarder rotation (R3). The method adds an assistant imaging channel comprising a linear polarization array and light source to the classical full-Stokes imaging optical path. Further, an alternating iterative algorithm of the polarization information matrix is used to solve the rotation angle of the phase retarder to obtain the full-Stokes information of the imaging target. Theoretical analysis, numerical simulations, and comparative experiments are conducted to verify that the proposed method can achieve accurate full-Stokes imaging measurements via R3. To the best of our knowledge, this is the first time that a full-Stokes imaging method with high precision performance has been proposed that does not depend on accuracy of rotation angle.

Flow mechanism of Gaussian light-induced vortex motion inside a nanofluid droplet

PurposeThe purpose of this study is to use a weak light source with spatial distribution to realize light-driven fluid by adding high-absorbing nanoparticles to the droplets, thereby replacing a highly focused strong linear light source acting on pure droplets.Design/methodology/approachFirst, Fe3O4 nanoparticles with high light response characteristics were added to the droplets to prepare nanofluid droplets, and through the Gaussian light-driven flow experiment, the Marangoni effect inside a nanofluid droplet was studied, which can produce the surface tension gradient on the air/liquid interface and induce the vortex motion inside a droplet. Then, the numerical simulation method of multiphysics field coupling was used to study the effects of droplet height and Gaussian light distribution on the flow characteristics inside a droplet.FindingsNanoparticles can significantly enhance the light absorption, so that the Gaussian light is enough to drive the flow, and the formation of vortex can be regulated by light distribution. The multiphysics field coupling model can accurately describe this problem.Originality/valueThis study is helpful to understand the flow behavior and heat transfer phenomenon in optical microfluidic systems, and provides a feasible way to construct the rapid flow inside a tiny droplet by light.

Study about photoinduction-based technology for trapping small brown planthopper

To provide a theory to guide the selection of the illumination parameters of light emitting diode (LED)-based light sources used for trapping Laodelphax striatellus, we used LED light sources and devices built in-house to detect L. striatellus phototactic behavior. Through phototaxis screening experiments of different light sources and the comparative experimental method, we analyzed the response patterns of L. striatellus to wavelength, light intensity, layout, flash frequency of monochromatic light sources, as well as combined color light sources, and discussed the mechanisms of the phototactic behavior of L. striatellus under different light sources. The results of the monochromatic light experiment showed that the trapping rate of the L. striatellus to the linear blue light source of 460 nm was the highest and was also significantly affected by the light intensity. The results of the experiments with the combined color light sources showed that compared with the linear 460 nm blue light source, the trapping rate of the L. striatellus was significantly improved by the polychromatic light, and the blue–green light led to the best improvement, reaching 1.5 times that of the trapping rate in the case of monochromatic light sources. The wavelength composition, light intensity, shape, and flash frequency of the light source used in this study can provide a theoretical basis for the development of LED-based light traps specifically for L. striatellus.

Application of Microspectral Imaging in Motor and Sensory Nerve Classification.

Objective It aimed to explore the application of the microscopic hyperspectral technique in motor and sensory nerve classification. Methods The self-developed microscopic hyperspectral acquisition system was applied to collect the data of anterior and posterior spinal cord sections of white rabbits. The joint correction algorithm was employed to preprocess the collected data, such as noise reduction. On the basis of pure linear light source index, a new pixel purification algorithm based on cross contrast was proposed to extract more regions of interest, which was used for feature extraction of motor and sensory nerves. Besides, the ML algorithm was employed to classify motor and sensory nerves based on feature extraction results. Results The joint correction algorithm was adopted to preprocess the data collected by the microscopic hyperspectral technique, so as to eliminate the influence of the incident light source and the system and improve the classification accuracy. The axon and myelin spectrum curves of the two kinds of nerves in the stained specimens had the same trend, but the values of all kinds of spectrum of sensory nerves were higher than those of motor nerves. However, the myelin sheath spectrum curves of motor nerves in the unstained specimens were greatly different from the curves of sensory nerves. The axon spectrum curves had the same trend, but the axon spectrum values of sensory nerves were higher than those of motor nerves. The ML algorithm had high accuracy and fast speed in motor and sensory nerve classification, and the classification effect of stained specimens was better than that of unstained specimens. Conclusion The microscopic hyperspectral technique had high feasibility in sensory and motor nerve classification and was worthy of further research and promotion.

Study on information content of light field on the object surface under various coherent states illumination

A novel approach for the measurement of information content of light field on the object surface illuminated by various coherent states source based on the statistical optics theory and Shannon’s information theory has been proposed. Firstly, we propose that the information content of light field on the object surface can be regarded as the product of the spacial freedom degrees of the object surface itself and that of the illuminating light field arriving at the object surface. Then, calculate the distribution of complex degree of coherence on the object surface under various coherent states illumination and then obtain the number of uncorrelated areas of light field on the object surface which can be used to determine the number of freedom degree of the light field. At the same time, taking into account the structure of the object itself, the freedom degree of the light field on the object surface in completely coherent, partially coherent and incoherent illumination are derived respectively.The specific algorithms for the information content of the light field illuminated by a 1D linear incoherent light source and uniform quasi monochromatic incoherent surface light source with arbitrary shape are also presented.

Medium-temperature furnace baking of 1.3 GHz 9-cell superconducting cavities at IHEP

Recently, heat treatment in the range of 250 °C–500 °C has been attempted with the aim of improving the quality factor (Q) of superconducting radio-frequency (SRF) cavities worldwide. Herein, medium-temperature (mid-T) furnace baking experiments were conducted at the Institute of High Energy Physics to obtain higher Q values. First, 1.3 GHz 1-cell cavities received mid-T furnace baking at different temperatures, resulting in not only the improvement of Q but also an anti-Q-slope behavior. Furthermore, mid-T furnace baking was applied to six 1.3 GHz 9-cell cavities, all of which indicated higher Q and anti-Q-slope behavior. The average Q was 3.8 × 1010 at 16 MV m−1. The maximum gradients of the 9-cell cavities were 22.7–26.5 MV m−1. Finally, the mid-T furnace baked 1.3 GHz 9-cell cavities were welded with helium vessel, with no degradation in the vertical tests. In addition, the mid-T furnace baking process was simplified in comparison with European X-ray Free Electron Laser and Linear Coherent Light Source because of the cancellation of light electro-polishing. This simplification is beneficial in the mass production of SRF cavities with high Q, which are widely adopted in free electron lasers and high-energy colliders.

P‐4.5: A New Light‐Guiding Structure for Optimizing the Uniformity of Side‐in Display Source

In this paper, a new light‐guiding structure for light source of side‐in display products is presented. Under the condition of using LED (Light Emitting Diode) as light source and 8mm pitch, using this structure, a uniform side‐in linear plane light source can be obtained within a light‐mixing distance of 5mm, and 75% uniformity can be achieved. The design of this structure is based on the principle of total reflection and the idea of peak‐load shifting, made of PC (Polycarbonate) material. Compared to traditional LGP (light guide plate), using this structure, uniform plane light source can be obtained in a shorter distance. It is especially suitable for products with front light source and transparent display. Besides, it can be bent or profiled to meet the requirements of narrow frame and special‐shaped products.

Techniques for studying materials under extreme states of high energy density compression

The properties of materials under extreme conditions of pressure and density are of key interest to a number of fields, including planetary geophysics, materials science, and inertial confinement fusion. In geophysics, the equations of state of planetary materials, such as hydrogen and iron, under ultrahigh pressure and density provide a better understanding of their formation and interior structure [Celliers et al., “Insulator-metal transition in dense fluid deuterium,” Science 361, 677–682 (2018) and Smith et al., “Equation of state of iron under core conditions of large rocky exoplanets,” Nat. Astron. 2, 591–682 (2018)]. The processes of interest in these fields occur under conditions of high pressure (100 GPa–100 TPa), high temperature (>3000 K), and sometimes at high strain rates (>103 s−1) depending on the process. With the advent of high energy density (HED) facilities, such as the National Ignition Facility (NIF), Linear Coherent Light Source, Omega Laser Facility, and Z, these conditions are reachable and numerous experimental platforms have been developed. To measure compression under ultrahigh pressure, stepped targets are ramp-compressed and the sound velocity, measured by the velocity interferometer system for any reflector diagnostic technique, from which the stress-density of relevant materials is deduced at pulsed power [M. D. Knudson and M. P. Desjarlais, “High-precision shock wave measurements of deuterium: Evaluation of exchange-correlation functionals at the molecular-to-atomic transition,” Phys. Rev. Lett. 118, 035501 (2017)] and laser [Smith et al., “Equation of state of iron under core conditions of large rocky exoplanets,” Nat. Astron. 2, 591–682 (2018)] facilities. To measure strength under high pressure and strain rates, experimenters measure the growth of Rayleigh–Taylor instabilities using face-on radiography [Park et al., “Grain-size-independent plastic flow at ultrahigh pressures and strain rates,” Phys. Rev. Lett. 114, 065502 (2015)]. The crystal structure of materials under high compression is measured by dynamic x-ray diffraction [Rygg et al., “X-ray diffraction at the national ignition facility,” Rev. Sci. Instrum. 91, 043902 (2020) and McBride et al., “Phase transition lowering in dynamically compressed silicon,” Nat. Phys. 15, 89–94 (2019)]. Medium range material temperatures (a few thousand degrees) can be measured by extended x-ray absorption fine structure techniques, Yaakobi et al., “Extended x-ray absorption fine structure measurements of laser-shocked V and Ti and crystal phase transformation in Ti,” Phys. Rev. Lett. 92, 095504 (2004) and Ping et al., “Solid iron compressed up to 560 GPa,” Phys. Rev. Lett. 111, 065501 (2013), whereas more extreme temperatures are measured using x-ray Thomson scattering or pyrometry. This manuscript will review the scientific motivations, experimental techniques, and the regimes that can be probed for the study of materials under extreme HED conditions.

Modification of the interaction of an electron with its own radiation field in photonic crystals with high-refractive layers

The self-energy interaction of atoms placed in air voids of one-dimensional photonic crystals with high-refractive layers is considered. Modification of the interaction of an electron with its own radiation field in the photonic crystal medium gives rise to a correction to its mass and kinetic energy. We demonstrate the photonic density of states of the periodic structure and the dependence of the mass correction of the valence electron of hydrogen atom and the alkali metals on the refractive index of the one-dimensional photonic crystal based on alternating amorphous hydrogenated layers of silicon nitride a-SiN x : H and vacuum, and layers of the high refractive index metamaterial consisting of Au nanoparticles with a dielectric matrix based on HfO2 and vacuum. The tunability of these materials gives rise to the tunability of the mass correction over a wide range. It is shown that the effect under study leads to significant shifts in the energy levels of atoms which is important for controlling physical and chemical processes, creating new linear light sources, and He-Ne-like lasers.

A Model of Diameter Measurement Based on the Machine Vision

If the shaft diameter can be measured in-situ during the finishing process, the closed-loop control of the shaft diameter processing process can be realized and the machining accuracy can be improved. Present work studies the measurement of shaft diameter with the structured light system composed of a laser linear light source and a camera. The shaft is a kind of part with rotationally symmetric structure. When the linear structured light irradiates the surface of the shaft, a light stripe will be formed, and the light stripe is a part of the ellipse. Therefore, the in-situ measurement of the shaft diameter can be realized by the light stripe and the rotational symmetry of the shaft. The measurement model of shaft diameter is established by the ellipse formed by the intersection of the light plane and the measured shaft surface. Firstly, in the camera coordinate system, normal vector of the light plane and the coordinates of the ellipse center are obtained by the calibration; then, the equation of oblique elliptic cone is established by taking the ellipse as the bottom and the optical center of the camera as the top. Next, the measurement model of shaft diameter is obtained by the established oblique elliptic cone equation and theoretical image plane equation. Finally, the accuracy of the measurement model of shaft diameter is tested by the checkerboard calibration plate and a lathe. The test results show that the measurement model of shaft diameter is correct, and when the shaft diameter is 36.162mm, the speed is 1250r/min, the maximum average measurement error is 0.019mm. The measurement accuracy meets the engineering requirement.

Frequency-Modulated Continuous-Wave LIDAR and 3D Imaging by Using Linear Frequency Modulation Based on Injection Locking

We propose and demonstrate a frequency modulated continuous-wave (FMCW) light detection and ranging (LiDAR) system, which employs double-sideband modulation combining with injection-locking to generate triangular linear frequency modulation light source. A fiber laser working as master laser is modulated by a Mach-Zehnder modulator to produce two first-order sidebands with tuning range of 8–14 GHz, one of which is extracted and amplified by a slave distributed feedback laser. A large carrier suppression ratio up to 20 dB is realized. The experiment results show the spatial resolution of the proposed LiDAR is 2.5 cm, equaling to the theoretical value. The velocity measurement is also performed by extracting Doppler shift. Finally, by combining the proposed LiDAR with 2-axis mechanical galvanometer scanner, the 3D imaging with high precision is realized, and the real scene is well restored. The proposed LiDAR system realizes pure linear frequency modulation without complex linearization algorithm or clock sampling circuit, and has advantages of simple structure and high precision.