Background
Measuring wound dimensions is important for monitoring and predicting the healing process. In our paper we propose and validate a handheld measuring system with dedicated software for ...measuring wound dimensions.
Methods
The measuring system comprises a commercial DSLR camera and a light pattern projection system. It is based on triangulation and structured illumination principles which enable handheld measuring. An edge of the wound is detected from the colour information of the measurement. Across the area of the wound, virtual healthy skin is approximated which enables the calculation of the wound volume and area, in addition to the wound circumference, which is calculated from the detected edge.
Results
In vitro verification using virtual standards showed that the accuracy of the analysis software is over 95% and 93% for measuring the area and volume respectively. A significant part of the error can be attributed to the inability of approximation to replicate entirely missing features. The accuracy of measuring the volume reduced to about 89% when a 3D measuring step was included in the analysis. When measuring in vivo wounds, the unrepeatability of the system was under 8% for measuring the area, which is a bit lower than comparable systems, and 5% for measuring the volume, which is about 4 times lower.
Conclusion
Based on these results and the ease of use, we conclude that the system is suitable to be used in daily clinical practice for measuring wound dimensions.
In this investigation, we used high-speed shadow photography to observe fast optodynamic phenomena such as shock waves and the ablation of flat metal surfaces. These phenomena were induced in air by ...a Q-switched Nd:YAG laser (
λ
= 1,064 nm) with a pulse duration of 4 ns and an excitation pulse energy between 10 and 55 mJ. For a good spatial resolution of the shadowgraphs, we used short illumination pulses (30 ps) from a frequency-doubled Nd:YAG laser (
λ
= 532 nm). Using the shadowgraphs of the shock wave expansion into a half-space, we measured the optodynamic energy conversion efficiency, defined as the ratio between the mechanical energy of the shock wave and the excitation pulse energy. This efficiency increases with an increasing excitation pulse energy. We also present the characteristic shadowgraphs of the ablation of a black-painted metal surface, where the macroscopic material particles are clearly visible. They follow the shock wave and eventually overtake it. As a result, the shape of the shock wave, which normally expands concentrically into the half-space, has an altered form. The presented results reveal the phenomenon of the laser ablation of coated metal surfaces.
Real-time 3D visualization of the breathing displacements can be a useful diagnostic tool in order to immediately observe the most active regions on the thoraco-abdominal surface. The developed ...method is capable of separating non-relevant torso movement and deformations from the deformations that are solely related to breathing. This makes it possible to visualize only the breathing displacements. The system is based on the structured laser triangulation principle, with simultaneous spatial and color data acquisition of the thoraco-abdominal region. Based on the tracking of the attached passive markers, the torso movement and deformation is compensated using rigid and non-rigid transformation models on the three-dimensional (3D) data. The total time of 3D data processing together with visualization equals 20 ms per cycle. In vitro verification of the rigid movement extraction was performed using the iterative closest point algorithm as a reference. Furthermore, a volumetric evaluation on a live subject was performed to establish the accuracy of the rigid and non-rigid model. The root mean square deviation between the measured and the reference volumes shows an error of ±0.08 dm3 for rigid movement extraction. Similarly, the error was calculated to be ±0.02 dm3 for torsional deformation extraction and ±0.11 dm3 for lateral bending deformation extraction. The results confirm that during the torso movement and deformation, the proposed method is sufficiently accurate to visualize only the displacements related to breathing. The method can be used, for example, during the breathing exercise on an indoor bicycle or a treadmill.
We examine the effects of the synchronized delivery of multiple Er:YAG-laser pulses during vapor-bubble oscillations into water. For this purpose, we used a laser beam transmission probe that enables ...monitoring of the bubble’s dynamics from a single shot. To overcome the main drawbacks of this technique, we propose and develop an appropriate and robust calibration by simultaneous employment of shadow photography. By using the developed experimental method, we show that the resonance effect is obtained when the second laser pulse is delivered at the end or slightly after the first bubble’s collapse. In this case, the resonance effect increases the mechanical energy of the secondary bubble’s oscillations and prolongs their duration. The presented laser method for synchronized delivery of Er:YAG-laser pulses during bubble oscillations has great potential for further improvement of laser endodontic treatment, especially upon their safety and efficiency.
Shadow photography and laser-induced breakdown spectroscopy (LIBS) are studied as methods for monitoring the selective removal of thin (i.e., under 100 μm) layers by laser ablation. We used a laser ...pulse of 5 ns and 16 mJ at 1064 nm to ablate an 18-μm-thin copper layer from the fiberglass substrate. On the basis of shadowgraphs of the laser-induced shock waves, we measured the optodynamic energy-conversion efficiency, defined as the ratio between the mechanical energy of the shock wave and the excitation-pulse energy. Our results show that this efficiency is significantly higher for the laser pulse–copper interaction than for the interaction between the excitation pulse and the substrate. LIBS was simultaneously employed in our experimental setup. The optical emission from the plasma plume was collected by using a spectrograph and recorded with a streak camera. We show that advancing of laser ablation through the copper layer and reaching of the substrate can be estimated by tracking the spectral region between 370 and 500 nm. Therefore, the presented results confirm that LIBS method enables an on-line monitoring needed for selective removal of thin layers by laser.
The present paper reports a new setup for acquisition of shape data for weldpieces during pulsed laser welding. The setup is based on illumination of the weldpiece surface by laser light, which is ...structured as multiple light planes, and acquisition of the image of the illuminated surface by a digital camera. The position of the optical system is fixed relative to the measured weldpiece. The acquired image is fed into a personal computer where it is processed to obtain the three-dimensional shape of the part of the weldpiece surface that was imaged by the camera. A setup that allows up to 20 shape measurements per second was developed based on this principle. The setup was applied to examine distortion of weldpieces during laser welding of low carbon thin steel sheets. According to the results the setup allows a rapid and accurate temporally and spatially resolved evaluation of weldpiece distortion.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
In this paper we present a novel approach to monitoring the deformations of a steel plate's surface during various types of laser processing, e.g., engraving, marking, cutting, bending, and welding. ...The measuring system is based on a laser triangulation principle, where the laser projector generates multiple lines simultaneously. This enables us to measure the shape of the surface with a high sampling rate (80 Hz with our camera) and high accuracy (+/-7 microm). The measurements of steel-plate deformations for plates of different thickness and with different illumination patterns are presented graphically and in an animation.
A laser anamorph profilometer Jezersek, M; Mozina, J
Strojniski Vestnik,
01/2003, Letnik:
49, Številka:
2
Journal Article
Recenzirano
This paper presents the principle, development, calibration and testing of a laser anamorph profilometer. A profilometer is based on the laser-triangulation principle with a laser plane projecting on ...the surface and digital processing of the acquired images. A lens with anamorph optics is used to fit the vertical measuring range and, consequently, to increase the vertical resolution. The system excels in terms of its robust and modular construction, its precision and uniquely designed calibration procedure, and its ability to make fast and reliable measurement.
This paper deals with a laser-cleaning process for removing a layer of paint. The effects of each individual laser pulse were monitored by a three-probe system. Ultrasonic signals from the rear ...surface of the substrate were obtained using an arm compensated Michelson interferometer, the optoacoustic waves in the surrounding air were detected using a laser beam deflection probe and the shape of the growing crater was measured using a laser anamorph profilometer. Two different cleaning lasers were used: an Excimer and a Nd:YAG laser. Typical parameters of the optodynamic signals versus the laser-pulse number are presented. A linear correlation between the quantity of ablated material and the integral of the ultrasonic signals was found together with an exponential relationship between the time-of-flight of the optoacoustic signals and the decoating rate.
We present a novel approach to monitoring the surface deformations during various types of laser processing, e.g., engraving, marking, cutting, bending, and welding. The measuring system is based on ...a laser triangulation principle, where the laser projector generates multiple lines simultaneously. This enables us to measure the shape of the surface with a high sampling rate (80 Hz with our camera) and high accuracy (+/-7 pm). Full-field measurements of steel-plate deformations are presented for plates of different thickness and with different processing parameters.
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