Light Plane Research Articles

Development of an In-Situ Laser Machining System Using a Three-Dimensional Galvanometer Scanner

Abstract In this study, a three-dimensional (3D) in-situ laser machining system integrating laser measurement and machining was built using a 3D galvanometer scanner equipped with a side-axis industrial camera. A line structured light measurement model based on a galvanometer scanner was proposed to obtain the 3D information of the workpiece. A height calibration method was proposed to further ensure measurement accuracy, so as to achieve accurate laser focusing. In-situ machining software was developed to realize time-saving and labor-saving 3D laser processing. The feasibility and practicability of this in-situ laser machining system were verified using specific cases. In comparison with the conventional line structured light measurement method, the proposed methods do not require light plane calibration, and do not need additional motion axes for 3D reconstruction; thus they provide technical and cost advantages. The in-situ laser machining system realizes a simple operation process by integrating measurement and machining, which greatly reduces labor and time costs.

Evaluation of Physiological Parameters and Effectiveness of an Immobilization Protocol Using Etorphine, Azaperone, and Butorphanol in Free-Ranging Warthogs (Phacochoerus africanus).

Twenty free-ranging warthogs (Phacochoerus africanus) in the Kruger National Park, South Africa, were immobilized with a combination of etorphine (0.039 ± 0.005 mg/kg) and azaperone (0.44 ± 0.06 mg/kg) administered intramuscularly by dart. Butorphanol (1 mg per mg etorphine) was administered intravenously at t = 5 min. A standardized scoring system was used to record induction, immobilization and recovery characteristics. Physiological parameters were recorded at 5 min intervals and an arterial sample collected for blood gas analyses every 15 min. At 45 min after butorphanol administration, immobilization was partially reversed by administering naltrexone (40x etorphine dose in mg) intravenously. Overall, induction quality was good, with the mean time to safe handling 5.9 ± 1.4 min. The majority of immobilization scores (54%) over the entire monitoring period (40 min) were at level 3, consistent with a light plane in which palpebral and laryngeal reflexes were still present but the animal could be safely handled. Overall mean heart rate was 94.7 ± 15.3 beats per min, mean respiratory rate was 14.7 ± 9.8 breaths per min, and the mean rectal temperature was 38.5 ± 1.0°C. Significant hypoxia (overall mean oxygen arterial partial pressure 38.8 ± 8.4 mmHg), hypercapnia (mean carbon dioxide arterial partial pressure 63.3 ± 7.8 mmHg), and acidosis (mean pH 7.28 ± 0.04) were observed in immobilized warthogs. Following antagonist administration, warthogs were standing within 1.0 ± 0.4 min, with the majority of recoveries scored as excellent. The drug combination proved to be effective in the immobilization of free-ranging warthogs with rapid induction and recovery, but with significant cardio-respiratory changes. Therefore, this drug combination may be useful when rapid immobilization and recovery are indicated, but should be used cautiously in compromised warthogs.

Tiling light sheet selective plane illumination microscopy using discontinuous light sheets.

Tiling light sheet selective plane illumination microscopy (TLS-SPIM) improves the 3D imaging ability of SPIM by using real-time optimized tiling light sheets. However, the imaging speed decreases and the raw image size increases due to the tiling process and additional camera exposures. The decreased imaging speed and the increased raw data could cause significant problems when TLS-SPIM is used to image large specimens at high spatial resolutions. Here, we present a novel method to solve the problem. Discontinuous light sheets created by scanning coaxial beam arrays synchronized with the detection camera rolling shutter are used in TLS-SPIM for 3D imaging. It improves the imaging efficiency of TLS-SPIM by reducing the number of tiles required per image plane without influencing the spatial resolution. We investigate the method via numerical simulations and experiments. We demonstrate the imaging ability of the TLS-SPIM using discontinuous light sheets and show the improved imaging efficiency by imaging optically cleared mouse brain.

Development of a novel line structured light measurement instrument for complex manufactured parts.

This paper studies a novel structured light measurement instrument for complex manufactured parts. In this research, a quick and accurate light plane calibration method and a novel light strip center extraction method were used to establish the measurement instrument. First, the intrinsic and external parameters of the camera are calibrated by Zhang's method. Second, a novel light plane calibration technique is proposed by using the original parameters and images in the process of camera calibration, which can be used to improve the accuracy of the measurement system because both the camera calibration and light plane calibration are based on the same target. Third, a subpixel extraction method is presented to extract the light strip center on the basis of the geometric center method. Finally, the constructed instrument is used to detect the geometric information of the complex manufactured parts. The experimental results show that the maximum measurement error is 0.1 mm under a measurement range of 50 mm and the accuracy is 0.2%, which indicates that the measurement instrument is fast, robust, and accurate enough to be applied to many kinds of measurements, such as railroad track deformation, the inner wall of a pipe, and so on.

Three-dimensional shape measurement technique for large-scale objects based on line structured light combined with industrial robot

Three-dimensional(3-D) shape measurement for large-scale objects based on line structured light combined with industrial robot has been increasingly important because of its attributes of high-flexibility and high-robustness. To acquire the shape of large-scale objects, the line structured light obtained 3-D lines are stitched together by using robot hand-eye calibration results. However, in the line structured light technique, the traditional light plane calibration is complex and the result 3-D measurement accuracy is relatively low. Besides, because the light plane equation of the line structured light is arbitrary, the traditional standard ball hand-eye calibration method cannot be directly used. In this paper, a light plane calibration method is proposed by using binocular cameras, which simplifies the calibration process and improves the 3-D measurement accuracy. Furthermore, a modified space circle fitting method is proposed for the standard ball hand-eye calibration, which can be flexibly combined with the line structured light for arbitrary light plane. Based on the above improvement of the light plane calibration and the robot hand-eye calibration, the proposed measurement technique can accurately measure 3-D shape for large-scale objects. Theoretical analysis and experiments are provided to evaluate its performance.

Optical cryostat with sample rotating unit for polarization-sensitive terahertz and infrared spectroscopy

We developed an optical cryostat with a sample-rotation unit for polarization-sensitive measurement in terahertz (THz) and infrared (IR) ranges. The cryostat, in combination with two metal-grid polarizers, provides full control of mutual orientation of the sample’s crystallographic axes and the light polarization plane. Importantly, this control is realized in-situ , i.e., during the sample cooling–heating cycle. To demonstrate the abilities of the developed cryostat, we used it in combination with a laboratory-made THz time-domain spectrometer, for polarization-sensitive measurements of an orthoferrite (YFeO3) in the range of 5 to 50 cm − 1. These measurements revealed strong angular dependence of the sample transmission. The developed cryostat is capable for solving numerous demanding problems of THz and IR spectroscopy in condensed matter physics and materials science, biophysics, chemical, and pharmaceutical sciences.

Imaging the developing human external and internal urogenital organs with light sheet fluorescence microscopy

Technological advances in three-dimensional (3D) reconstruction techniques have previously enabled paradigm shifts in our understanding of human embryonic and fetal development. Light sheet fluorescence microscopy (LSFM) is a recently-developed technique that uses thin planes of light to optically section whole-mount cleared and immunolabeled biologic specimens. The advent of commercially-available light sheet microscopes has facilitated a new generation of research into protein localization and tissue dynamics at extremely high resolution. Our group has applied LSFM to study developing human fetal external genitalia, internal genitalia and kidneys. This review describes LSFM and presents our group's technique for preparing, clearing, immunostaining and imaging human fetal urogenital specimens. We then present light sheet images and videos of each element of the developing human urogenital system. To the extent of our knowledge, the work conducted by our laboratory represents the first description of a method for performing LSFM on the full human urogenital system during the embryonic and fetal periods.

Achromatic polarization rotator with tunable rotation angle

We theoretically suggest and experimentally demonstrate a broadband composite optical rotator that is capable of rotating the polarization plane of a linearly-polarized light at any chosen angle. The device is composed of an even number of half-wave plates (WPs) rotated at specific angles with respect to their fast-polarization axes. The frequency bandwidth of the polarization rotator in principal increases with the number of half-WPs. Here we experimentally examine the performance of rotators composed of two, four, six, eight and ten half-WPs.

On the application of a supercontinuum white light laser for simultaneous measurements of temperature and velocity fields using thermochromic liquid crystals

Simultaneous velocity and temperature measurements using thermochromic liquid crystals (TLC) as tracer particles are discussed, with regard to measuring range, uncertainty and spatial resolution. For the first time, a supercontinuum laser is used to illuminate these particles, which shall later be used for the characterization of the momentum and heat transfer in Rayleigh-Bénard cells with high aspect ratio using particle image velocimetry (PIV) and particle image thermometry (PIT). Light scattered from the TLCs is analyzed by spectrometer measurements, revealing its general scattering characteristics depending on the angle between the light sheet plane and the viewing axis. It is shown that white light sources with continuous spectral characteristic and a slightly higher fraction of light in the red wavelength range perform well, thereby the supercontinuum white light laser can be used, even though it has a cut-in wavelength of about 475 nm. The numerical aperture of the detection optics and chromatic aberrations of the laser light significantly affect the temperature sensitivity and dynamic range of the color of the TLCs. This may cause an effective temperature sensitivity range of about one-tenth of their nominal range, particularly at large angles between light sheet plane and viewing axis, as usually applied in PIV. A simultaneous velocity and temperature measurement in a Rayleigh-Bénard cell experimentally validates that the use of the supercontinuum laser allows for reliable simultaneous PIV and PIT measurements with high spatial resolution of less than 500 µm in out-of-plane direction, on condition that an appropriate two-dimensional calibration is applied.

Post-natal development of EEG responses to noxious stimulation in pigs (Sus scrofa) aged 1-15 days

AbstractThis study examined electroencephalographic (EEG) indices of acute nociception in pigs (Sus scrofa) aged 1, 5, 7, 10, 12 and 15 days, post-natal. Ten pigs per age were anaesthetised with halothane in oxygen and maintained at a light plane of anaesthesia. EEG was recorded bilaterally using a five-electrode montage. Following a 10-min baseline period, tails were docked using side-cutter pliers and recording continued for a further 5 min. Changes in the median frequency (F50), 95% spectral edge frequency (F95) and total power (PTOT) of the EEG were used to assess nociception. Tail-docking at one day of age induced no significant changes in the EEG spectrum. A typical nociceptive response, characterised by an increase in F50 and decrease in PTOT was evident at ten days of age, with five and seven day old pigs exhibiting responses in either F50 or PTOT only. Pooling of data into ≤ 7 days of age and > 7 days of age revealed F50 was higher overall in the older group. Whilst PTOT decreased after docking in both groups, this response was larger and more prolonged in the older group. F95 increased after docking in the older pigs only. Overall, these data provide evidence of an increase in cortical responsiveness to noxious stimulation with increasing post-natal age, suggesting there may be qualitative differences in pain perception between age groups. Further, the data provide some support for current recommendations that tail-docking and other painful husbandry procedures be performed within seven days of birth in order to minimise their impact on animal welfare.

Activating an anterior nucleus gigantocellularis subpopulation triggers emergence from pharmacologically-induced coma in rodents

Multiple areas within the reticular activating system (RAS) can hasten awakening from sleep or light planes of anesthesia. However, stimulation in individual sites has shown limited recovery from deep global suppression of brain activity, such as coma. Here we identify a subset of RAS neurons within the anterior portion of nucleus gigantocellularis (aNGC) capable of producing a high degree of awakening represented by a broad high frequency cortical reactivation associated with organized movements and behavioral reactivity to the environment from two different models of deep pharmacologically-induced coma (PIC): isoflurane (1.25%–1.5%) and induced hypoglycemic coma. Activating aNGC neurons triggered awakening by recruiting cholinergic, noradrenergic, and glutamatergic arousal pathways. In summary, we identify an evolutionarily conserved population of RAS neurons, which broadly restore cerebral cortical activation and motor behavior in rodents through the coordinated activation of multiple arousal-promoting circuits.

Optical hygrometer using light-sheet skew-ray probed multimode fiber with polyelectrolyte coating

The measurement of humidity provides valuable information to a range of industries. Existing hygrometers lack the combination of high sensitivity/low detection-limit, temperature insensitivity, fast response, high robustness and low cost. We present a new design of humidity sensors based on the combination of a polymer-coated multimode fiber interrogated by a light sheet (i.e. thin plane of light) designed to precision excite the optimum group of skew rays for enhanced sensitivity. The sensing mechanism is water absorption of light via evanescent-wave interaction mediated by a polymer-coated multimode fiber. For a 10.0 bilayer poly(diallyldimethylammonium) (PDDA)/poly(styrenesulfonate) (PSS)-coated sensing fiber, we demonstrated a sensitivity of up to 0.14 dB/%RH/cm, a detection limit of 0.007%RH, a temperature cross-sensitivity of less than ˜0.13%/°C, and response/recovery times of 115 ms and 200 ms. The tested dynamic range is between 10%RH and 94%RH. The dependence on the total optical power rather than the phase of light makes such sensors relatively insensitive to temperature while remaining sensitive to humidity. The PDDA/PSS functional coating inherently offers fast response. The use of multimode fibers and power meters make such fiber-optic sensors highly robust and relatively inexpensive, easing the translation to practical applications.

Alfaxalone total intravenous anaesthesia in dogs: pharmacokinetics, cardiovascular data and recovery characteristics

ObjectiveTo evaluate the cardiovascular effects, pharmacokinetic (PK) data and recovery characteristics of an alfaxalone constant rate infusion (CRI) of different duration in dogs at manufacturer’s recommended dose rate. Study designExperimental, prospective, randomized, crossover study. AnimalsSix intact female Beagles. MethodsFollowing an intravenous alfaxalone bolus (3 mg kg–1), anaesthesia was maintained using an alfaxalone CRI at 0.15 mg kg–1 minute–1 for 90 (short CRI) or 180 minutes (long CRI). Venous blood samples were collected to determine the PK profile. Cardiovascular variables and recovery characteristics were evaluated. Recovery was scored on a scale ranging from 0, excellent to 4, bad. A mixed-model statistical approach was used to compare the cardiovascular parameters (global α = 0.05). An analysis of variance was performed to compare PK parameters and recovery times between treatments. ResultsNo significant difference was noted between protocols for any PK parameter. Volume of distribution at steady state (935.74 ± 170.25 versus 1119.15 ± 190.65 mL kg–1), elimination half-life (12 ± 2 versus 13 ± 3 minutes), clearance from the central compartment (26.02 ± 4.41 versus 27.74 ± 5.65 mL kg–1 minute–1) and intercompartmental clearance (8.47 ± 4.06 versus 12.58 ± 7.03 mL kg–1 minute–1) were comparable for short CRI and long CRI. Cardiovascular variables remained within physiological limits. Mechanical ventilation was necessary (short CRI: n = 1, long CRI: n = 4). The manufacturer’s recommended dose rate resulted in a light plane of anaesthesia. No significant differences in recovery times and scores were observed between treatments. The quality of recovery was scored as very poor with both protocols. Conclusions and clinical relevancePK data were similar between long and short infusions of alfaxalone at the manufacturer's recommended dose, with acceptable cardiovascular conditions. Nevertheless, both protocols resulted in a superficial plane of general anaesthesia with poor recovery characteristics.

Optical Rotation Approach to Search for the Electric Dipole Moment of the Electron

The P , T -odd Faraday effect (i.e., rotation of the polarization plane of light propagating through a medium in presence of the external electric field due to P , T symmetry violating interactions) is considered for several atomic species: Ra, Pb, Tl, Hg, Cs, and Xe. Corresponding theoretical simulation of P , T -odd Faraday experiment, with already achieved intracavity absorption spectroscopy characteristics and parameters, is performed. The results show that the magnetic dipole transitions in the Tl and Pb atoms as well as the electric dipole transitions in the Ra, Hg and Cs atoms are favorable for the observation of the P , T -odd Faraday optical rotation. The estimation of the rotation angle of the light polarization plane demonstrates that recently existing boundaries for the electron electric dipole moment can be improved by one-two orders of magnitude.

Comparison of Caudal Block vs. Penile Block in Terms of Surgical Incision Response for Circumcision and Postoperative Analgesia Requirements

Circumcision is a frequently performed surgery in children worldwide. For circumcision, penile and caudal epidural blocks are commonly used. Nerve blocks not only decrease the systemic analgesia requirements intra-operatively but also increase the length of pain relief postoperatively. The aim of the present study was to compare the surgical incision response in circumcision, in children with a caudal block and penile block. We also compared the systemic analgesic requirements postoperatively in both groups.
 Materials and Methods: The study was conducted in pediatric patients. Total of 30 samples (n = 30) was taken and divided into two groups of 15 each. The group A received caudal block and group B received penile block. The blocks were performed after general anesthesia. We tried our best to eliminate all the factors which can lead to tachycardia (such as hypoxia, light plane of anesthesia, hyperthermia and hypothermia, hypercarbia, hypovolemia etc). The patients were keenly observed for change in heart rate on incision, the heart rates were recorded before and at incision (surgical incision response) in both groups. The postoperative consumption of the pain killers were also noted in both the groups.
 Results: We observed that the patients in group A with caudal block did not show any significant surgical response, whereas in group B patients with penile block showed increased heart rate at the incision. There was no complain of pain in group A in the recovery period. Whereas complains of pain were recorded in most of the children in group B, hence pain killers were given to the patients in this group.
 Conclusion: Our data proved that the caudal block was better than the penile block in terms of pain relief.

Groove Depth Detection Method Base on the Line Laser Vision Measurement on Cement Concrete Pavement

The groove depth has a decisive influence on the anti-sliding performance of cement concrete pavement, and it also plays an important role on the noise of cement concrete pavement. Aiming the shortcomings of traditional measurement methods of groove depth detection on the cement concrete pavement, a measurement method base on the structure light vision model was proposed. This method was realized by that the groove depth was obtained by 3D coordinate of the light strip according to the camera model and the structure light plane equation. A new algorithm based on double 2D plane pane target was proposed as the key step of this method.

Extrinsic parameters calibration of multi-camera with non-overlapping fields of view using laser scanning.

An extrinsic parameters calibration method of multi-cameras with non-overlapping fields of view (FOV) using laser scanning is presented. Firstly, two lasers are mounted on a multi-degree-of-freedom manipulator and can scan objects freely by the projected line-structured light. Then, controlling the movement of the manipulator, the line-structured light is projected into the field of view of one of the multi-cameras, and the light plane equation in the camera coordinate frame is calibrated by the target. The manipulator is moved several times in small amplitude to change the position of structured light in the field of vision of the camera and to continue to calibrate the light plane. The light plane equation of line-structured light in the manipulator coordinate frame are solved by the hand-eye calibration method. Secondly, with the help of the light planes, projected into the field of vision of other cameras to be calibrated, the light plane equation in the camera coordinate frame is calibrated, and the external parameters between the camera coordinate frame and the manipulator coordinate frame are calculated, so that the calibration of the external parameters of multiple cameras can be realized. The proposed method connects the non-overlapping multi-cameras by the laser scanning. It can effectively solve the problem of multi-camera extrinsic parameter calibration under the conditions of long working distance and complex environment light.

Propensity rules in photoelectron circular dichroism in chiral molecules. I. Chiral hydrogen

Photoelectron circular dichroism results from one-photon ionization of chiral molecules by circularly polarized light and manifests itself in forward-backward asymmetry of electron emission in the direction orthogonal to the light polarization plane. What is the physical mechanism underlying asymmetric electron ejection? How "which way" information builds up in a chiral molecule and maps into forward-backward asymmetry? We introduce instances of bound chiral wave functions resulting from stationary superpositions of states in a hydrogen atom and use them to show that the chiral response in one-photon ionization of aligned molecular ensembles originates from two propensity rules: (i) Sensitivity of ionization to the sense of electron rotation in the polarization plane. (ii) Sensitivity of ionization to the direction of charge displacement or stationary current orthogonal to the polarization plane. In the companion paper we show how the ideas presented here are part of a broader picture valid for all chiral molecules and arbitrary degrees of molecular alignment.

Propensity rules in photoelectron circular dichroism in chiral molecules. II. General picture

Photoelectron circular dichroism results from one-photon ionization of chiral molecules by circularly polarized light and manifests itself in forward-backward asymmetry of electron emission in the direction orthogonal to the light polarization plane. To expose the physical mechanism responsible for asymmetric electron ejection, we first establish a rigorous relation between the responses of unaligned and partially or perfectly aligned molecules. Next, we identify a propensity field, which is responsible for the chiral response in the electric-dipole approximation, i.e. a chiral response without magnetic interactions. We find that this propensity field, up to notations, is equivalent to the Berry curvature in a two-band solid. The propensity field directly encodes optical propensity rules, extending our conclusions regarding the role of propensity rules in defining the sign of forward-backward asymmetry from the specific case of chiral hydrogen to generic chiral systems. Optical propensity rules underlie the chiral response in photoelectron circular dichroism. The enantiosensitive flux of the propensity field through the sphere in momentum space determines the forward-backward asymmetry in unaligned molecules and suggests a geometrical origin of the chiral response. This flux has opposite sign for opposite enantiomers and vanishes for achiral molecules.

Congenital bilateral laryngeal paralysis in a 10-month-old English springer spaniel

This report describes a 10-month-old female, English springer spaniel that was referred to the surgical department for investigation of progressive exercise intolerance and stridor. After performing a complete blood test,...