The study of the roundness and cylindricity deviations of parts produced with the use of the additive manufacturing.

The paper is dedicated to the evaluation of the accuracy of rotary parts produced with the use of advanced manufacturing technology. The authors investigated the impact of the layer thickness of the applied material and the orientation of the model when printing using the PolyJet method™ on the geometrical quality of manufactured products. To analyze the influence of the assumed factors on the geometrical quality of the holes, a novel evaluation method has been developed. The proposed method takes into account parameters such as roundness deviation, profile irregularity coefficient, dominant harmonic component of the roundness profile, cylindricity deviation, diameter error, and surface topography parameters. The study presented in this paper had two main objectives. The former was to analyze the impact of the layer thickness of the applied material and the orientation of the model when printing using the PolyJet method™ on the geometrical quality of rotary parts. The latter objective was to test a novel, multi-parametric method of evaluation of the accuracy of produced parts in practice. The results obtained by the authors prove that the new evaluation method can be useful in the assessment of the accuracy of manufactured products.

Fast and accurate polarimetric calibration of infrared imaging polarimetric sensors.

Polarimetric imaging cameras require polarimetric calibration to accurately estimate the incident Stokes vector of incoming radiation. This calibration establishes a relationship between changes in the sensor signal and incident Stokes vector. In the standard procedure, an imager is presented with a set of input Stokes vectors with two different radiance values. In the long-wavelength infrared (LWIR) and mid-wavelength infrared bands, blackbodies with different temperatures are used for each set of Stokes vectors. The radiometric offset is subtracted, and standard radiometric or nonuniformity correction procedures are performed in a separate step. This paper proposes an alternative all-in-one approach that combines radiometric calibration, nonuniformity correction, and polarimetric calibration. The standard and proposed methods are compared for a division-of-time LWIR polarimeter. The proposed calibration method achieves an RMS error of 0.34% compared with the conventional technique's error of 0.83%, yielding a factor of 2.4 improvement in the reconstructed accuracy of a linear Stokes vector; in addition, it is less time-consuming and less prone to ambient temperature fluctuations than the typical two-point method. The method also accounts for beam wander and narcissus effects and enables simple, straightforward polarimetric measurement.

Local Effects of a 1940 nm Thulium-Doped Fiber Laser and a 1470 nm Diode Laser on the Pulmonary Parenchyma: An Experimental Study in a Pig Model.

The lungs are a common site of metastases from malignant tumors. Their removal with a minimal but safe tissue margin is essential for the long-term survival of patients. The aim of this study was to evaluate the usefulness of a 1940 nm thulium-doped fiber laser (TDFL) and a 1470 nm diode laser (DL) in a pig model of lung surgery that involved the incision and excision of lung tissue. Histopathological analysis was performed on days 0 and 7 after surgery. Neither TDFL nor DL caused significant perioperative or postoperative bleeding. Histological analysis revealed the presence of carbonized necrotic tissue, mixed fibrin-cellular exudate in the superficial zone of thermal damage and bands of deeper thermal changes. The mean total width of thermal damage on day 0 was 499.46 ± 61.44 and 937.39 ± 109.65 µm for TDFL and DL, respectively. On day 7, cell activation and repair processes were visible. The total width of thermal damage was 2615.74 ± 487.17 µm for TDFL vs. 6500.34 ±1118.02 µm for DL. The superficial zone of thermal damage was narrower for TDFL on both days 0 and 7. The results confirm the effectiveness of both types of laser in cutting and providing hemostasis in the lungs. TDFL caused less thermal damage to the lung parenchyma than DL.

Usefulness of Thulium-Doped Fiber Laser and Diode Laser in Zero Ischemia Kidney Surgery-Comparative Study in Pig Model.

BACKGROUND: The aim of this study was to evaluate the usefulness of a thulium-doped fiber laser and a diode laser in zero ischemia kidney surgery, by carrying out a comparative study in a pig model. MATERIAL AND METHODS: Research was carried out on 12 pigs weighing 30 kg each. A thulium-doped fiber laser (TDFL) and a diode laser (DL) operating at wavelengths of 1940 and 1470 nm, respectively, were used. The cut sites were assessed both macroscopically and microscopically. The zone of thermal damage visible in the histopathological preparations was divided into superficial and total areas. RESULTS: During partial nephrectomy, moderate to minimal bleeding was observed, which did not require additional hemostatic measures. All animals survived the procedure. On day 0, the total thermal damage depth was 837.8 µm for the TDFL and 1175.0 µm for the DL. On day 7, the depths were 1556.2 and 2301.7 µm, respectively. On day 14, the overall thermal damage depth for the DL was the greatest (6800 µm). The width of the superficial zone was significantly reduced on days 7 and 14 after TDFL application. CONCLUSION: Both lasers are suitable for partial wedge nephrectomy without ischemia in pigs. The TDFL produced similar or better hemostasis than the DL, with a smaller zone of thermal damage and, therefore, seems more suitable for application in human medicine.

Mueller matrix of imaging polarimeter's optical system-comparison of simulation results obtained using Zemax and MATLAB software with experimental data.

A procedure for simulating the Mueller matrix of an optical system across the field of view of a long-wavelength infrared (LWIR) imaging polarimeter is presented in this paper. The procedure is based on a ray-tracing model and uses off-the-shelf software and custom add-on procedures written in MATLAB. A simulation was conducted to obtain polarization ray tracing across the entire surface of the focal-plane array for a set of wavelengths within the LWIR (8-14 µm) window and within the instrument's field of view of 7.3∘×5.5∘ with a set of different starting polarization states. Finally, the simulation results are compared with measurement data obtained from the home-designed optical train of a polarimetric camera. For Mueller matrix entries significantly larger than zero, both simulation and experiment results show high consistency, with overall RMS error of less than 2%. The presented results are useful when anticipation of a Mueller matrix of an imaging polarimeter is of high importance.

Method of signal processing in a time-division LWIR image polarimetric sensor.

We report on the method of signal processing in a passive long-wave infrared (LWIR) image polarimetric sensor. The method enables the detection of natural and manmade targets. It includes the error related to the rotation of the polarizing element during an image reading as well as permits the polarimeter operation without a classical phase synchronization loop. In addition, to verify the proposed method, a prototype of a time-division polarimetric system that operates in the 8-12 µm band and is based on an uncooled microbolometric detector array was designed and developed. The entire system enabled us to successfully detect a few types of artificial objects from the distance of several tens of meters. The maximum image refresh rate was 5.45 Hz and could be further increased.

Comparison of A 1940 nm Thulium-Doped Fiber Laser and A 1470 nm Diode Laser for Cutting Efficacy and Hemostasis in A Pig Model of Spleen Surgery.

Partial and total splenectomies are associated with a high risk of substantial blood loss. Lasers operating at wavelengths strongly absorbed by water have the potential to improve hemostasis and cut while providing a narrow zone of thermal damage. The aim of this study is to compare a thulium-doped fiber laser (TDFL) emitting a wavelength of 1940 nm and a diode laser (DL) operating at 1470 nm for spleen surgery in a pig model. A partial splenectomy and spleen incisions were made in 12 animals using the two laser devices. The hemostasis was evaluated visually during surgeries. Post-mortem and histopathological evaluations were done on days 0, 7, and 14 following surgery. Neither TDFL nor DL caused bleeding on day 0 or delayed bleeding. On day 14, pale streaks at the site of incision were slightly wider after cutting with DL than with TDFL. Histological analysis revealed a carbonized zone with exudation and a deeper zone of thermal tissue damage on day 0. The width of the thermal changes was 655.26 ± 107.70 µm for TDFL and 1413.37 ± 111.85 µm for DL. On day 7, a proliferation of fibroblasts and splenocytes was visible, as well as a formation of multinucleated giant cells adjacent to the residues of carbonization. The zone of thermal damage was broader for DL (1157.5 ± 262.77 µm) than for TDFL (682.22 ± 116.58 µm). On day 14, cutting sites were filled with connective and granulation tissues with the residues of carbonization. The zone of thermal damage was narrower for TDFL (761.65 ± 34.3 µm) than for DL (1609.82 ± 202.22 µm). Thus, both lasers are efficient in spleen surgery, providing good hemostasis. However, TDFL produces a narrower zone of thermal damage, which suggests its better efficiency for spleen surgery, especially when performing more precise procedures.

Preliminary Evaluation of Thulium Doped Fiber Laser in Pig Model of Liver Surgery.

Partial liver resection is a treatment of choice for liver tumors; the range of parenchyma excision varies from a small part of the tissue surrounding the neoplasm up to 70% of the organ. One of the major concerns during liver resection is blood loss. Thulium lasers which are characterized by the length of emission wave corresponding to a peak absorption of water create a new possibility of cutting tissues efficiently with minimal thermal damage and concurrently providing a good hemostasis control. The aim of our study was to evaluate an impact of liver transection with thulium doped fiber laser on an intraoperative bleeding and histopathological changes during postoperative period in swine model. Ten animals were subjected to open surgery partial liver resection and an incision of liver tissue with an all-fiber, diode-pumped, and continuous-wave Tm3+-doped fiber laser emitting 37.4 W of output power at ~1.94 µm wavelength. The macroscopic and histopathological evaluation was performed intraoperatively as well as 7 and 14 days after surgery. Macroscopically almost no bleeding was observed during surgery and no signs of bleeding were stated after 7 and 14 days. Histopathological analysis of the transection margin revealed a thermal damage area ranging in depth from 620.23 ± 23.82 µm on the day of surgery to 1817.70 ± 211.98 µm after 7 days. In the samples taken intraoperatively and after 7 days a superficial zone of carbonization was visibly separated from the deeper changes. After 14 days one 765.35 µm deep zone characterized by a granulation was present. In conclusion, thulium doped fiber laser is efficacious in cutting with a narrow zone of thermal injury and provides a good hemostasis during liver transection, thus being a potential tool for oncotic liver surgery.

Mid-infrared, super-flat, supercontinuum generation covering the 2-5 µm spectral band using a fluoroindate fibre pumped with picosecond pulses.

Broadband, mid-infrared supercontinuum generation in a step-index fluoroindate fibre is reported. By using ~70-picosecond laser pulses at 2.02 µm, provided by an optical parametric generator, a wide spectrum with a cut-off wavelength at 5.25 µm and a 5-dB bandwidth covering the entire 2-5 µm spectral interval has been demonstrated for the first time. The behaviour of the supercontinuum was investigated by changing the peak power and the wavelength of the pump pulses. This allowed the optimal pumping conditions to be determined for the nonlinear medium that was used. The optical damage threshold for the fluoroindate fibre was experimentally found to be ~200 GW/cm2.

High-power supercontinuum generation in a ZBLAN fiber with very efficient power distribution toward the mid-infrared.

We report high-power supercontinuum (SC) generation in a step-index fluorozirconate (ZBLAN) fiber with a zero-dispersion wavelength shifted to ~1.9 µm. Pumping the fluoride fiber with 2.75 W of power provided by a thulium-doped fiber amplifier, a continuous spectrum extending from ~0.85 to 4.2 µm with 2.24 W of average output power was achieved. Over 61% (1.37 W) of the total output power corresponds to wavelengths longer than 3 µm, which shows, to the best of our knowledge, the highest power conversion efficiency toward the mid-IR spectral band in relation to the output spectrum width. A linear SC power scalability up to 5.24 W, with a spectral band of ~0.9-4 µm, with repetition rate and pump power provided by a 1.55 µm fiber master-oscillator power amplifier system, is also demonstrated.

Generation of self-mode-locked resembling pulses in a fast gain-switched thulium-doped fiber laser.

We report on a generation of self-starting mode-locked resembling (MLR) pulses in an all-fiber, gain-switched Tm(3+)-doped fiber laser operating at 2 µm wavelength, which we believe to be the first demonstration of such an approach. The laser delivers 100% modulated MLR pulses within an envelope of ~30 ns gain-switched pulse at a repetition rate of 30 kHz. The maximum average output power is 0.4 W and the maximum peak-power of MLR pulses can be as high as 1.1 kW. The performance of the laser is described.

Mid-IR supercontinuum generation in a ZBLAN fiber pumped by a gain-switched mode-locked Tm-doped fiber laser and amplifier system.

We demonstrate a novel method of mid-infrared (mid-IR) supercontinuum (SC) generation with the use of a 2 µm gain-switched self-mode-locked thulium-doped fiber laser. SC radiation ranging from ~1.9 to 3.8 µm wavelength, generated in a single-mode ZBLAN fiber with a zero-dispersion wavelength (ZDW) shifted to ~1.9 µm, is reported. An average output power of 0.74 W with 0.27 W at wavelengths longer than 2.4 µm was measured. It is, to the best of our knowledge, the first report on such an approach to generate a mid-IR SC in optical fibers.

Actively Q-switched and mode-locked Tm3+-doped silicate 2 µm fiber laser for supercontinuum generation in fluoride fiber.

A diode-pumped actively Q-switched and actively mode-locked Tm3+-doped double-clad silicate fiber laser is reported providing up to 5 W of average output power at ~60 kHz Q-switch envelope repetition rate and ~8 µJ subpulses with up to 2.4 kW peak power. Using this source as a pump laser for supercontinuum generation in a ZBLAN fiber, over 1080 mW of supercontinuum from 1.9 µm to beyond 3.6 µm was obtained at an overall efficiency of 3.3% with respect to the diode pump power.

Simulation of reflected and scattered laser radiation for designing laser shields.

This paper presents a computer simulation of reflected and scattered laser radiation for calculating the angle of laser shields performed with the Laser Shield Solver computer program. The authors describe a method of calculating the shield angle for laser shields which protect workers against reflected and scattered laser radiation and which are made from different materials. The main assumptions of the program, which calculates and simulates reflected laser radiation from any material and which can be used for designing shield angles, are presented. Calculations are compared with measurements of reflected laser radiation. The results for one type of laser and different materials which interacted with a laser beam showed that the Laser Shield Solver was an appropriate tool for designing laser shields and its simulations of reflected laser radiation distribution have practical use.

Electrooptically Q-switched mid-infrared Er:YAG laser for medical applications.

An actively Q-switched Er:YAG laser generating pulses at 2.94 microm has been developed and investigated. For a single Er:YAG generator at 3 Hz repetition rate, pulses of 91.2 ns duration and 137 mJ energy have been obtained. It corresponds to pulse train with high-peak power of ~ 1.5 MW. For 10 Hz repetition rate 30 mJ of output energy in single pulse has been achieved. These results, according to our knowledge, are the best world-wide achievements.