Parallel Light Research Articles

Motion deviation rectifying method of dynamically measuring rail wear based on multi-line structured-light vision

Rail wear dynamic measurement techniques are important to ensure the security of railway system and the efficiency of maintaining. Nowadays, a widely used approach is based on structured-light vision sensor, which includes a camera and a laser projector generating a light plane on the inner side of the rail. Considering the sensor installation error and vibration of running train, it is difficult to ensure the perpendicularity between the light plane and the rail, which leads to large measurement error. In order to overcome the problem, a motion deviation rectifying method is proposed. Rail section profiles are obtained by a multi-line structured-light vision sensor with multiple parallel light planes. Each profile can be segmented into two curves. One representing the rail waist is used to fit the rail longitudinal axis (parallel to train running direction) and establish an auxiliary plane perpendicular to the direction. Deviation rectifying process is to project the rail section profiles onto the auxiliary plane to recover perpendicularity between the light plane and the rail. Then another curve representing the rail head is used to calculate the rail wear based on the standard profile. The experimental results indicate that the method reduces the rail wear measurement error, meeting the requirements for real-time dynamic measurement of rail wear.

Out-standing! Om Dansk Tennis Club og tennisspilleren Leif Rovsing

Out-standing! Danish Tennis Club and the Tennis Player Leif RovsingOn April 13, 1917 the Danish newspaper B.T. published an article about the nationally renowned Danish tennis player, Leif Rovsing, who was planning to build a magnificent tennis hall. Personally funding the project, he referred to the tennis hall as a ‘World-Sports-Establishment’ to be built on land he had found close to Copenhagen. On May 5, 1917 the Danish Football Association (DBU) excluded Rovsing from all clubs under their auspices and banned him from participating in all Danish tournaments due to “presumed homosexuality”. This was the starting point for Rovsing to realise the dream he had described in B.T. In cooperation with architect Henry Madsen he built the out-standing tennis hall, Dansk Tennis Club. From an architectural point of view, the 43,5 m long and 23,5 m wide tennis hall is an original piece of sports architecture worldwide, with its smallmuntined windows, providing the hall with an intake of daylight, which sheds a soft parallel light over the courts without blinding the players. The hall also came into being with a gentleman’s study, plush sofas, china over the doors, and wall decorations from Egypt and Bali. It is these unexpected juxtapositions that made Dansk Tennis Club so unusual at the time – and to this day.

Development of a CCD-Based Optical Computed Tomography Scanner Used in 3D Gel Dosimetry

This study proposed a CCD-based (charge-coupled device) optical computed tomography scanner (CT-s2) for 3D gel dosimetry. A parallel laser light was generated to pass through the gel sample using a diffuser and collimating lens. A CCD was used to capture projection image of gel sample at each step. An image reconstruction algorithm, filtered-back projection (FBP) technique was used to reconstruct the 3D image. Two better rotational steps are suggested as 1.0 degree and 1.5 degree for considering both of angular resolution and position deviation. The un-irradiated and irradiated BANG gel samples were scanned and reconstructed using FBP technique. Some artifacts were found in reconstructed images. Some discussions for artifacts were conducted and some solutions provided by previous researches to reduce these artifacts will be evaluated in the future work.

Design of an Optical Mechanical System for High-Resolution Encoders

An optical mechanism composed of a movable part and a fixed part for the increment high-resolution optical displacement encoders is proposed in this paper. The parallel light emitted from the movable part passes through a double-concave lens and a specially designed optical grating; it is then projected onto a phototransistor array receiver to indicate the displacement of the movable part. The relationship equation of the lens is developed to design an optical mechanism which can enlarge the displacement so that it becomes observable. Based upon the simulation results, a specially designed optical grating is designed to compensate for the deviations on the detecting surface and to derive the increment movement of the light source. The simulation results indicated that the optical mechanism with 50 times magnification could make the 10 nm movement intervals of a light source be about 500 nm movement intervals in the detecting surface. Furthermore, an experimental system with a 200 nm resolution is established to verify the possibility of the proposed structure.

Shape from Endoscope Image based on Photometric and Geometric Constraints

An endoscope is a medical instrument that acquires images inside the human body. This paper proposes a new approach to recover 3-D shape under conditions of both point light source illumination and perspective projection. Previous approaches recovered shape based on a Fast Marching Method under conditions of parallel light source and orthographic projection. The new approach uses optimization based on constraints provided by geometry and by a suitable image irradiance equation. Experiments with endoscope images are demonstrated to confirm that the recovered shape is improved.

并行共焦测量中的并行光源技术综述

Parallel confocal measurement technology changes traditional simple scanning into a multi-spot scanning,and it will improve the efficiency of measurement significantly. In this paper,the working principle of confocal measurement technology is introduced and some methods to produce a parallel light source in the parallel confocal measurement are surveyed. Then,it analyzes the advantages and disadvantages of these methods. At last,it presents the latest research achievements,and describes new methods to produce the parallel light source based on the micro lens array and the Digital Micro-lens Device( DMD). By analysis of the mechanism of spatial light modulation,it establishes a laser parallel astigmatism measuring system based on a parallel light source and dual beam paths.

The Micro-Indentation Detection of Multilayer Structured Transparent Film Based on Dark Field Illumination

It is difficult to keep the precise conveyance in film discontinuous winding system, while there are no etch or print marks on the transparent film. Based on dark field illumination theory, a micro-indentation detection method is proposed for multilayer structured transparent film roll-to-roll processing. Two parallel strip lights are involved in the vision system to illuminate the indentation at a low angle, which ensures that the distinct image of the cutting indentation can be obtained in reflection and diffuse homogeneous lights. The measurement of micro-indentations can be used to evaluate the film conveying positioning accuracy and calculate the compensation of film feeding position control. An experiment platform was established to show the efficiency and feasibility of proposed scheme. Experimental results showed that the micro-indentation detection method, based on dark field illumination, is successful to increase the feeding precision of multilayer structured transparent film discontinuous winding system.

A new static lighting concentrator with optical coupler

Currently, energy-saving and carbon dioxide reduction are the most critical issues faced by the globe. Therefore, solar energy should be used as much as possible. A possible use is to illuminate a solar cell so as to transform light energy directly into electricity. However, due to its low efficiency and high cost, the solar cell is not presently economically feasible. Utilization of solar energy, which is considered one of the most important renewable energy sources, not only reduces consumption of fossil fuel but also slows down the pace of global warming. In addition to the use of solar cells, daylight illumination is also an important access to solar energy. Our team has developed a technique that can guide the natural light to the interior for indoor illumination. It is called the “Natural Light Guiding System.” Our system can guide sunlight to the interior, but the distribution of light at the exit of the system is disordered. To solve this problem, we have proposed an optical coupling transmission structure with right-angled prism collecting modules. We analyzed the mathematical model of coupling transmission. And, we also analyzed the efficiency of this cascade structure at the exit surface of the concentrator. In this paper, we provide a high efficiency new concentrator coupled to a transmission device. We save 75% of the optical fiber cable expense usage and we improve efficiency by 47.46% when we add an optical coupling transmission structure to our static lighting concentrator. It is better than the original cascade prism static concentrator. Taking the fiber cost into consideration, we defined a key performance index—it is a ratio of luminous flux on an illuminated area. Our system can provide more powerful light for indoor illumination than existing methods The optical coupling can provide high transmission efficiency and provide parallel light beams at the export from the optical coupling module. We used optical simulation tools to design and simulate the efficiency of the active module. We can use this system as an ecological illumination system to offer steady illumination in indoor space to provide healthy illumination, save energy, and meet safety requirements.

Fabrication of micro-nano surface texture by CsCl lithography with antireflection and photoelectronic properties for solar cells

A pyramid and nanopillar micro-nano surface texture of silicon wafer, which has pyramid arrays about 4–8μm with different nanopillars of average diameter from 100 to 500nm and height from 500nm to 1.5μm, is fabricated by Cesium Chloride (CsCl) self-assembly lithography and dry etching for solar cell. This micro-nano surface texture with 100 and 200nm average diameter has very good antireflection with reflectance below 5% for the wavelength ranging from 400 to 1000nm and much lower than that of single pyramid or nanopillar arrays with the same average diameter. The reflected distribution of this micro-nano structure illuminated with white parallel light at incidence angle of 45° is tested by a irradiatometer at the reflected angle from 10 to 80 degree and shows a total diffuse and very low reflection at different reflected angles, which benefits from both the advantages of nanopillar and pyramid structure. The solar cell with this micro-nano texture has been finished with thermal diffusion of Phosphorus for P–N junction and printing silver plasma for front electrode poles, and its photovoltaic conversion efficiency is about 7.05% which is higher than that of solar cell only with the planar, single pyramid or nanopillar and made with the same fabricating process.

Variation in seed dormancy in Echinochloa and the development of a standard protocol for germination testing. II: Breaking dormancy in seeds unresponsive to light or dark conditions alone by using heat and ethanol pretreatment

A recently established method for the germination of Echinochloa seeds recognised and accounted for variation in responses to light and darkness. This method used parallel light and dark tests and was successful in promoting germination in most seed lots. However, some samples exhibited deeper dormancy and were not fully responsive to either test. In the present study, we employed warm pretreatments where seeds were exposed to dilute aqueous ethanol solutions to attempt to break their dormancy. Based on tests of five Echinochloa accessions, we propose a new, follow-up protocol that can be used on samples unresponsive to the established method. The additional step involves a 3-day dark pretreatment at 35-37°C, imbibing the seeds in ~0.25M ethanol (aq). After this pretreatment, the seeds should be germinated for 14 days at 20/30°C (16 hours/ 8 hours) with half held in darkness and the other half exposed to an 8-hour light cycle.

Height Measurement of Micro-Solder Balls on Metal Pad by White Light Projection

Micro-solder balls are commonly used in wafer-level ball grid array (BGA) packages as an interconnection medium. To measure the height of a micro-solder ball on a metal pad, we propose a white light projection method to avoid interference from pads in the shadow of the ball. The optical projection of a solder ball under the illumination of a parallel white light beam is studied, and the relationships between the ball height, ball radius, and shadow length are deduced. An experimental platform with a simple optical system and white light emitting diodes lighting source is constructed to obtain ball and shadow images, and a program developed to process these images and calculate the ball height. The heights of the balls on a BGA chip are measured using this new method, and the results verified using a commercial optical profiler. This method is not sensitive to the patterns on the substrate surface and has great potential for future application.

Photorefractive keratectomy (PRK) versus laser assisted in situ keratomileusis (LASIK) for hyperopia correction

Hyperopia, or hypermetropia (also known as long-sightedness or far-sightedness), is the condition where the unaccommodating eye brings parallel light to a focus behind the retina instead of on it. Hyperopia can be corrected with both non-surgical and surgical methods, among them photorefractive keratectomy (PRK) and laser assisted In situ keratomileusis (LASIK). There is uncertainty as to whether hyperopic-PRK or hyperopic-LASIK is the better method. The objectives of this review were to determine whether PRK or LASIK leads to more reliable, stable and safe results when correcting a hyperopic refractive error. We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (The Cochrane Library 2012, Issue 2), MEDLINE (January 1950 to February 2012), EMBASE (January 1980 to February 2012), Latin American and Caribbean Literature on Health Sciences (LILACS) (January 1982 to February 2012), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov (www.clinicaltrials.gov) and the WHO International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). There were no date or language restrictions in the electronic searches for trials. The electronic databases were last searched on 17 February 2012. When trials are included in the review we will search the reference lists of the studies included in the review for information about further trials. We will use the Science Citation Index to search for papers that cite any studies included in this review. We did not handsearch journals or conference proceedings specifically for this review. We planned to include only randomised controlled trials (RCTs) comparing PRK against LASIK for correction of hyperopia and then perform a sensitivity analysis of pre- and post-millennial trials since this is the mid-point in the history of both PRK and LASIK. We did not identify any studies that met the inclusion criteria for this review. As no studies met the inclusion criteria for this review, we discussed the results of non-randomised trials comparing hyperopic-PRK with hyperopic-LASIK. No robust, reliable conclusions could be reached, but the non-randomised trials reviewed appear to be in agreement that hyperopic-PRK and hyperopic-LASIK are of comparable efficacy. High quality, well-planned open RCTs are needed in order to obtain a robust clinical evidence base.

Pixel Art with Refracted Light by Rearrangeable Sticks

AbstractPixel art is a kind of digital art that through per‐pixel manipulation enables production of a diverse array of artistic images. In this paper, we present a new way for people to experience and express pixel art. Our digital art consists of a set of sticks made of acrylate resin, each of which refracts light from a parallel light source, in certain directions. Artistic users are able to easily rearrange these sticks and view their digital art through the refracted light projection on any planar surface. As we demonstrate in this paper, a user can generate various artistic images using only a single set of sticks. We additionally envision that our pixel art with rearrangeable sticks would have great entertainment appeal, e.g., as an art puzzle.

Determination of Interfacial Area in Gas-Liquid Two Phase by Light Transmission

The purpose of the present paper is to develop light beam method to measurement of interfacial area in a rectangular gas-liquid bubble column. Total interfacial area can be determined in bubble column filled by transparent liquid by light transmission method. According to pervious researches, the fraction of parallel light is function of interfacial area and optical path length that these two parameters imply Transmission Number or NT. The drop diameters were measured in the range of 2.2 to 5 mm, and in this range, the specific area is found to depend only upon the light transmission. Three different systems with various liquid phases have been used in this work. It had been proved that light transmission method for dilute suspension or stationary gas phase has a good consequence. In this work, good agreement between actual and calculated interfacial area proves that light transmission method would be able to determine interfacial area in multiple scattering, and it is possible to use earlier mathematic model to measure interfacial area in multiple scattering in gas-liquid bubble columns.

Laser sheet scattered light method for industrial measurement of thickness residual stress distribution in flat tempered glass

The paper presents the laser sheet scattered light technique, a fast optical non contact method for measuring internal stress distribution over a cross section of flat glass specimens, designed for closed loop control of glass tempering furnaces. The technique is an evolution of the scattered light method for flat glass residual stress analysis and allows a full thickness stress profile to be measured with a single shot acquisition across a glass plate without any contact. A linearly polarized laser sheet, shaped into a thin plane of parallel light beams, enters orthogonally to the side of the flat glass illuminating its full thickness. Light sheet is orthogonal to the glass surface and travels parallel to it. Stress induced birefringence through the glass affects light polarization, thus scattered light intensity detected at 90° with respect to the polarization of the incident light appears spatially modulated in intensity. A camera aligned orthogonal to the laser light polarization collects an image of fringes whose shape is digitally analyzed to measure the thickness stress state. The paper describes the development of this technique by recalling the scattered light method, then describing its automation by scanning a collimated beam across the glass thickness and finally by showing that the scan method can be substituted by the light sheet method. Light sheet method provides a full field non contact stress measurement across the glass thickness, thus allowing for a fast inspection method, suitable for industrial use. Flat glass items for industrial use have bevelled edges; this does not allow measurements close to glass surface. To solve this limit, experimental data are extrapolated by a symmetrical polynomial fitting and imposing a zero integral to the stress profile. Results on surface stress measured by the laser sheet scattered method are in agreement with those of the automated light scattered method and show a fair agreement with measurement by an epibiascope, thus proving the applicability of the method for fast and contact-less detection of residual thickness stress; the industrial application of the method is outlined, so that a tempering furnace could be controlled using feed-back data from thickness stress measurements on flat glass.

System of Measuring the Sub-Pixel Edge of Linear CCD Based on Multi-Scale Transform

In order to improve the precision, speed, integration and reliability of the linear CCD system, a multi-scale compress derivation edge detection method of one-dimension image based on wavelet multi-scale transform is presented in this paper. The inspecting system of defects in based on CCD obtains signals of defects in with irradiation of parallel light by using linear array CCD control circuit. The defect signals were collected and transferred by using virtual oscillograph DSO-2902, and the defect signals were analyzed and processed by using computer. Based on it, Before the CCD signal entered the edge detecting system, it had been filtered by filter. Utilizing the characteristic that the grads of grey scale breaks at the edge of picture, the pixel edge of picture was detected by the algorithm which can be used to detect the edge of picture automatically. multi-scale transform used to detect the sub-pixel edge of picture. This method which is more accurate than former single threshold level comparison method can enhance edge and remove noise effectively.

Synthesis of colloidal solutions of SrFe12O19 plate-like nanoparticles featuring extraordinary magnetic-field-dependent optical transmission

Hard-magnetic plate-like nanoparticles of SrFe12O19 were synthesised hydrothermally. The particles, fixed in a polymer, exhibited a coercivity in the range 0.9–1.8 kOe, and the saturation magnetization values reached 64 emu g−1. Electrostatically stabilized aqueous colloidal solutions of the plate-like particles with average thickness of 5–8 nm and average diameter of 30–80 nm were prepared. The nanoparticles readily oriented when applying a weak magnetic field as low as a few Oe, and due to the linear dichroism phenomena a strong change in the optical transmittance of the solution took place. The extinction coefficient ratio for the perpendicular and the parallel light's electric field vector relative to the magnetic field direction was found to be up to 4.5. The experimental results were compared with a theoretical model, in which the optical absorption of the nanoparticles was calculated from the polarizability of oblate ellipsoids.

线阵光学降水现象自动测量系统

An optical precipitation auto-measurement system based on a linear image sensor was designed to reveal the physical mechanism and essence of the precipitation.First,according to physical characteristics of precipitation particles and the demand for precipitation observation,an optical unit and a data acquisition and processing platform for the high speed linear image sensor were designed.As the mass acquisition data were inconvenient for transmission and processing under a continuous operation,the real-time binarization and encoding processing of the linear image were carried out by Field Programmable Gate Array(FPGA).To eliminate the influence of performance excursion of parallel light source and pixel photoelectric response nonuniformity on the setting thresholds and to ensure the measurement precision and coherence,an adaptive threshold setting scheme was proposed and realized based on a MicroBlaze soft-core processor in the FPGA.The comparison experiment with tipping bucket pluviometer based on calibration in a laboratory was carried out.Experimental result indicates that the resolution of precipitation auto-measurement system can achieve 0.1 mm,and the error of cumulative precipitation amount in synchronization observation is about 15%.Obtained results can satisfy the requirements of precipitation auto-measurement for stabilization and high precision.

Complete polarization control of light from a liquid crystal spatial light modulator

We present a method to generate complete arbitrary spatially variant polarization modulation of a light beam by means of a parallel aligned nematic liquid crystal spatial light modulator (SLM). We first analyze the polarization modulation properties in a transmission mode. We encode diffraction gratings onto the SLM and show how to achieve partial polarization control of the zero order transmitted light. We then extend the technique to a double modulation scheme, which is implemented using a single SLM divided in two areas in a reflective configuration. The polarization states of the transmitted beam from the first pass through the first area are rotated using two passes through a quarter wave plate. The beam then passes through the second area of the SLM where additional polarization information can be encoded. By combining previously reported techniques, we can achieve complete amplitude, phase and polarization control for the diffracted light that allows the creation of arbitrary diffractive optical elements including polarization control. Theoretical analysis based on the Jones matrix formalism, as well as excellent experimental results are presented.

Preparation and Characterization of Monocrystal Nano-Sliver Lamella

Monocrystal nano-sliver lamella were prepared by hydrothermal method with the precursor Ag2C2O4and the surface active agent polyvinyl alcohol (PVA). The influence of the dosage of PVA on the film thickness and yield of nano-sliver lamella (NSL) were analyzed. And the morphology, the film thickness and electron diffraction pattern of NSL were characterized by scanning electron microscopy (SEM) and transmission electron microscope (TEM) respectively . Furthermore,the same sample was respectively characterized by the parallel optical path and the focus optical path of X-ray diffraction (XRD), and the difference between the diffraction data of these two paths was compared. The results show that the dosage of PVA has significant effect on the thickness and yield of monocrystal nano-sliver lamella. The reason that the great difference between diffraction data of the parallel light path and focusing light path can be mainly owing to the preferential orientation in space of NSL.