Calibration of laser beam direction based on monocular vision

In the laser displacement sensors measurement system,the laser beam direction is an important parameter.Particularly,the azimuth and pitch angles are the most important parameters to a laser beam.In this paper,based on monocular vision,a laser beam direction measurement method is proposed.First,place the charge coupled device(CCD)camera above the base plane,and adjust and fix the camera position so that the optical axis is nearly perpendicular to the base plane.The monocular vision localization model is established by using circular aperture calibration board.Then the laser beam generating device is placed and maintained on the base plane at fixed position.At the same time a special target block is placed on the base plane so that the laser beam can project to the special target and form a laser spot.The CCD camera placed above the base plane can acquire the laser spot and the image of the target block clearly,so the two-dimensional(2D)image coordinate of the centroid of the laser spot can be extracted by correlation algorithm.The target is moved at an equal distance along the laser beam direction,and the spots and target images of each moving under the current position are collected by the CCD camera.By using the relevant transformation formula and combining the intrinsic parameters of the target block,the2D coordinates of the gravity center of the spot are converted to the three-dimensional(3D)coordinate in the base plane.Because of the moving of the target,the3D coordinates of the gravity center of the laser spot at different positions are obtained,and these3D coordinates are synthesized into a space straight line to represent the laser beam to be measured.In the experiment,the target parameters are measured by high-precision instruments,and the calibration parameters of the camera are calibrated by a high-precision calibration board to establish the corresponding positioning model.The measurement accuracy is mainly guaranteed by the monocular vision positioning accuracy and the gravity center extraction accuracy.The experimental results show the maximum error of the angle between laser beams reaches to0.04°and the maximum error of beam pitch angle reaches to0.02°.

Kinetics of Coil-to-Globule Transition of DansyI-Labeled Poly（N-isopropyl- acrylamide） Chains in Aqueous Solution

The coil-to-globule transition of thermally sensitive linear poly（N-isopropylacrylamide） （PNIPAM） labeled with dansyl group is induced by 1.54 μm laser pulses （widths10 ns）. The dansyl group is used to follow the transition kinetics because its fluorescence intensity is very sensitive to its micro-environment. As the molar ratio of NIPAM monomer to dansyl group increases from 110 to 300, the effect of covalently attached dansyl fluorophores on the transition decreases. In agreement with our previous study in which we used 8-anilino- l-naphthalensulfonic acid ammonium salt free in water as a fluorescent probe, the current study reveals that the transition has two distinct stages with two characteristic times, namely, Tfast≈0.1 ms, which can be attributed to the nucleation and formation of some ＂pearls＂ （locally contracting segments） on the chain, and tslow≈0.5 ms, which is related to the merging and coarsening of the ＂pearls＂.Tfast is independent of the PNIPAM chain length over a wide range （Mw=2.8× 10^6-4.2 × 10^7 g/mol）. On the other hand, Tslow only slightly increases with the chain length.

A Flexible Calibration Method of Laser Light-Sectioning System for Online 3D Measurement

A flexible calibration method based on a front-coated flat mirror is proposed for a laser light-sectioning three-dimensional(3D)measurement system. Since the calibration target and its mirror image are spatially separated and can be recorded in an image by a camera,the proposed method requires only a single composite image that contains a non-planar checkerboard pattern,a laser strip projected on the target and their mirror images to complete the calibration of the camera and the laser plane in one step. Levenberg-Marquardt(LM)algorithm is used to optimize the system parameters,and the measurement accuracy and speed are improved to enable online 3D inspection. Static and dynamic online 3D measurements are carried out on a cup and a triple stepped shaft,respectively,to validate the proposed method. The shaft has two steps with the depth of(0.5±0.01)mm and(2±0.01)mm to be measured online when the shaft is rotated and translated at the same time. The measurement results can be output at a frequency of 7 to 11 readings per second with standard deviations of 0.040 mm and 0.051 mm. The experimental results verify the effectiveness and flexibility of the proposed method.

Comparative study on different derivatization procedures for analysis of recombinant human erythropoietin by capillary electrophoresis with laser-induced fluorescence detection

Human erythropoietin （hEPO）, an endogenous glycoprotein, plays a fundamental role in erythropoiesis controlling the formation of red blood cells. Production of recombinant human erythropoietin （rhEPO） has made it possible for its abuse in competitive sports. In this work, pre-capillary and on-capillary derivatization by 5-furoylquinoline-3-carboxaldehyde （FQ） and fluorescein isothiocyanate （FITC） for the detection of rhEPO by capillary electrophoresis with laser-induced fluorescence detection （CE-LIF） were compared. FQ pre-capillary labeling improves sensitivity but degrades the glycoforms separation due to the inhomogeneity of the reaction products from multiple labeling. Compared with FITC pre-capillary derivatization with the excess fluorescent background, the on-capillary FQ derivatization method can provide shorter analysis time, lower background, and better selectivity. It is demonstrated that, through optimizing reaction conditions of FQ on-capillary derivatization, both high sensitivity and satisfactory resolution for the analysis of the be used for the glycoforms profiling and quality control of rhEPO doping control analysis. glycoforms of rhEPO could be obtained. This method can It may be used as a candidate method for fast screening in

Comparison Study of Two Commercial Spectrometers for Heavy Metal Analysis of Laser Induced Breakdown Spectroscopy （LIBS）

The purpose of this paper is to compare the performance of two spectrometers that are manufactured from the same company. In this work, heavy metals like lead Pb and copper Cu in the KBr matrix were analyzed using the laser induced breakdown spectroscopic technique. A Q-switched Nd：YAG laser with 90mJ per pulse operating at the fundamental wavelength of 1064nm and pulse duration of 10 ns was used to generate plasma at the focal region. The important experimental parameters such as the laser energy, integration time, distance between the lens and sample, distance and angle of the optical fiber from the target were optimized. Two spectrometers manufactured by Ocean Optics namely as Maya2000Pro and USB 4000 were employed for anlyzing the spectral lines. The experimental setup and conditions were remained the same for both experiments. The production of spectral lines from each of the interested elements was analyzed and compared with the NIST （National Institute of Standards and Technology） database. The sensitivity, repeatability and limit of detection for each of the systems are discussed in detail.