A real-time and accurate monitoring and identification method for explosion-proof instruments is proposed for industrial practical projects, and a monitoring and identification system for explosion-proof instruments based on machine vision is developed. Firstly, according to the location of the monitored explosion-proof instrument, the original image of the explosion-proof instrument is obtained, and the instrument dial is obtained by using machine vision technologies such as Gaussian filter, OTSU, weighted average method, etc. Grasp the position of the pointer through the ring ROI area, and finally correct the pointer angle by using the geometric relationship to identify the reading of ammeter and voltmeter on the instrument panel and identify the status of the indicator light by using the gray value difference. The experimental results show that this method can recognize the reading of the pointer in different instrument panels and different pointer positions, and the recognition rate is 98%. The status of the indicator is accurately identified. The system meets the needs of real-time online monitoring and identification.
Germanium material based on band gap engineering has aroused great interest for the CMOS-compatible optoelectronic integrated circuits due to its quasi-direct band gap structure. While many technologies have been conquered for germanium light, optimization is the bottleneck due to the excessive threshold current density, low luminescence efficiency and unstable problem in the laser device. The proper understanding of inter-valley scattering mechanisms between direct and indirect valleys in germanium is of paramount importance in view of the optimization of Ge as optical gain medium. The paper focuses on the inter-valley scattering mechanisms in strained Ge in theory based on a time-dependent Hamiltonian describing the electron-phonon interaction. The impacts of temperature and strain on the inter-valley scattering between direct and indirect valleys are discussed quantificationally. For the electrons in direct valley, emitting inter-valley phonon scattering is the dominant mechanism for momentum and energy relaxation of electrons both at the low and room temperature, and they are more likely to be scattered by inter-valley phonons to the L valleys with lower energy. For the electrons in L valleys, inter-valley scattering is important only for electrons with sufficient energy to scatter into the direct valley, which can happen in germanium devices under high electric field. Numerical results also indicate that enhanced indirect-to-direct inter-valley scattering and reduced direct-to-indirect inter-valley scattering are reliable by introducing tensile strain in Ge material at room temperature. The results offer fundamental understanding of phonon engineering for further optimization of the germanium light sources.
Localized surface plasmon based on coupled metallic nanoaggregates has been extensively studied in enhancing light scattering and optical force, which depends on the geometry/symmetry of plasmonic oligomers and the refractive index of surrounding medium. As the interparticle gap distance between nanoparticles becomes smaller than several nanometers, quantum effects can change the plasmon coupling in classical predictions. However, most of the research on plasmonic scattering and optical force has been done based on local calculations even for the gap below ~3 nm, in which the nonlocal screening plays a vital role. Here, we theoretically investigate the nonlocal effect on the evolution of plasmon resonance modes in strongly coupled nanoparticle dimer antennas with the gap down to 1 nm. Then, the refractive index sensing and optical force in this nonlocal system is evaluated and compared with the results in classical calculations. We find that in the nonlocal regime, both refractive index sensibility factor and optical force are actually smaller than their classical counterparts mainly due to the saturation of both plasmon-shifts and near-field enhancement. These results would be beneficial for the understanding of interaction between light and nonlocal plasmonic nanostructures and the development of plasmonic devices such as nanoantennas, nanosensors, and photonic manipulation.
In recent years, more and more Americans are diagnosed with prostate cancer, and the current detection methods still have some disadvantages. Photoacoustic imaging, as a new non-invasive imaging technique, has the capable of imaging complex tissue and owns the ability of early tumor imaging. And the photoacoustic signal of the tumor is bound up with its light energy distribution. In this paper, Monte Carlo method was used to simulate the light propagation in the prostate phantom. The pictures of light energy distribution by the irradiation of a pulsed laser were obtained. With the pulsed laser, according to the absorption coefficient of tumor, the local energy temporal changes in prostate can be illustrated. As we known, the local photoacoustic signal has a relationship with the change of light energy. Then we can see the influence of photoacoustic signal under the changes of the absorption coefficient of tumor.
Prostate cancer is one of diseases with high mortality in man. Many clinical imaging modalities are
utilized for the detection, grading and staging of prostate cancer, such as ultrasound, CT, MRI, etc. But
they lacked adequate sensitivity and specificity for finding cancer in transition or central zone of
prostate. To overcome these problems, we propose a photoacoustic imaging modality based on cylinder
diffuse radiation through urethra for prostate cancer detection. We measure the related parameters
about this system like lateral resolution (~2mm) and axial resolution(~333μm). Finally, simulated sample was imaged by our system. The results demonstrate the feasibility for detecting prostate cancer by our system.
The thyroid is one of the main endocrine glands of human body, which plays a crucial role in the body's metabolism.
Thyroid cancer mortality ranks only second to ovarian cancer in endocrine cancer. Routine diagnostic methods of thyroid
diseases in present clinic exist misdiagnosis and missed diagnosis to varying degrees. Those lead to miss the best period
of cancer treatment--early. Photoacoustic spectroscopy technology is a new tool, which provides an effective and
noninvasive way for biomedical materials research, being highly sensitive and without sample pretreatment. In this
paper, we use photoacoustic spectroscopy technology (PAST) to detect the absorption spectrum between normal and
malignant thyroid tissues. The result shows that the photoacoustic spectroscopy technology (PAST) could differentiate
malignant thyroid tissue from normal thyroid tissue very well. This technique combined with routine diagnostic methods
has the potential to increase the diagnostic accuracy in clinical thyroid cancer diagnosis.
Absorption coefficient of biological tissue is an important factor for photothermal therapy and photoacoustic imaging. However, its determination remains a challenge. In this paper, we propose a method using focusing photoacoustic imaging technique to quantify the target optical absorption coefficient. It utilizes the ratio of the amplitude of the peak signal from the top boundary of the target to that from the bottom boundary based on wavelet transform. This method is self-calibrating. Factors, such as absolute optical fluence, ultrasound parameters, and Grüneisen parameter, can be canceled by dividing the amplitudes of the two peaks. To demonstrate this method, we quantified the optical absorption coefficient of a target with various concentrations of an absorbing dye. This method is particularly useful to provide accurate absorption coefficient for predicting the outcomes of photothermal interaction for cancer treatment with absorption enhancement.
The photoacoustic (PA) signal attenuation was affected by many factors in an imaging system. In this presentation, the
factors lead to the signal attenuation and their characters were discussed based on tissue optics, acoustic transportation
and detection in a long-focal-zone PA imaging system. A method to recover the detected PA signals was presented and
employed to image a thyroid sample in vitro. The experimental results demonstrated that the method could be used to
improve the imaging depth and quality in the PA system.
The location and ischemia extent are two important parameters for evaluating the acute myocardial ischemia (AMI). A focused-transducer-based photoacoustic imaging method was employed to assess time-dependent AMI. Our preliminary results show that the photoacoustic signal could identify the myocardium. The intensity and area of photoacoustic images of myocardium could be used for characterizing the ischemia extent and scope of myocardial ischemia. The results also imply that the intensity and area of photoacoustic images are the rapid fall of an exponential model with an increase of delaying time after the left anterior descending coronary artery (LAD) occlusion. These experimental results were consistent with the clinical characteristics. The findings suggest that the photoacoustic imaging be a potential tool for the real-time assessment of acute myocardial ischemia during surgical operation.
We explore the feasibility of using photoacoustic imaging based on a focused transducer to characterizing acute
myocardial ischemia at different stage. In this study, we blocked rat left anterior coronary descending artery (LAD) to
induce the acute myocardial ischemia. The results show that the intensity and areas of photoacoustic images of
myocardial decrease with the LAD time increasing, which suggests that photoacoustic imaging has a potential for
diagnosis of acute myocardial ischemia.
Photoacoustic imaging is a promising technique in practical medicine to image biological tissue's function and diagnose
internal organs. In this paper, a new photoacoustic imaging modality for imaging internal organs was presented. A laser
which wavelength is tunable was coupled into a multimode optical fiber. And the fiber was inserted into the inner tract of
the samples to deliver light for exciting photoacoustic signals. The outgoing PA signal was detected by a focal ultrasound
transducer with long focal length which was placed on the surface of the samples. By transducer scanning, we obtained a
2D cross-section photoacoustic image. Finally, we evaluate this system's performance and demonstrate its capabilities by
imaging phantoms with complex structure.
KEYWORDS: Photoacoustic spectroscopy, Wavelets, Signal to noise ratio, Wavelet transforms, Signal analyzers, Transducers, Data acquisition, Interference (communication), Ultrasonics, Photoacoustic imaging
In this paper, we present the continuous wavelet analysis for extract the information of photoacoutical signal sampled
with a focoused transducer. The results demonstrate that wavelet transform of photoacoustic signals with 1 time
averaging could reconstruct the localization and the size of absorbers, and it greatly reduced the data acquisition time. In
addition, the results indicate that the localization and the size of absorbers could be recovered as the value of
signal-to-noise ratio (SNR) is in the range from 0.3 to1.
A new optical technique for continuous, noninvasive monitoring of blood glucose levels based on ultrasonic modulation
of scattering light is proposed. The ultrasound-modulated scattered light has an accurate separation of scattering and
absorption changes in tissue. And the optical scattering and absorbing coefficient of tissue depend on the concentration
of glucose in the extracellular fluid. As the glucose induced to scattering and absorption changes, the ultrasoundmodulated
light also changes. In this paper, a correlation is observed between ultrasound-modulated light intensity as
well as its modulation depth and blood glucose concentration in phantom experiments. In addition, some researches
about ultrasound-modulated signal affected by the temperature of glucose aqueous solution are done. Preliminary
experiments find that this method is a promising noninvasive blood glucose measurement.
This paper reports a combined speckle and polarization-difference approach for imaging absorbing inhomogeneities
embedded in optical scattering medium. Mathematical morphological operation has been used to suppress the speckle
coarse grains and reconstruct the position of the absorbing inhomogeneities embedded in turbid medium. Moreover, we
quantify the scattering coefficient of the background medium using the average granulometric size. Then the local
speckle contrast ratio is applied to enhance the edges of absorbing objects.
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