depth of field
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2022 ◽  
Vol 148 ◽  
pp. 107748
Author(s):  
Wenwen Wang ◽  
Shiyao Li ◽  
Penghui Liu ◽  
Yongai Zhang ◽  
Qun Yan ◽  
...  

2022 ◽  
Author(s):  
Peng Wu ◽  
Dejie Zhang ◽  
Jing Yuan ◽  
Shaoqun Zeng ◽  
Hui Gong ◽  
...  

Author(s):  
Wakana Saito ◽  
Masaaki Omura ◽  
Jeffrey A. KETTERLING ◽  
Shinnosuke Hirata ◽  
Kenji YOSHIDA ◽  
...  

Abstract In a previous study, an annular-array transducer was employed to characterize homogeneous scattering phantoms and excised rat livers using backscatter envelope statistics and frequency domain analysis. A sound field correction method was also applied to take into account the average attenuation of the entire scattering medium. Here, we further generalized the evaluation of backscatter coefficient (BSC) using the annular array in order to study skin tissues with a complicated structure. In layered phantoms composed of two types of media with different scattering characteristics, the BSC was evaluated by the usual attenuation correction method which revealed an expected large difference from the predicted BSC. In order to improve the BSC estimate, a correction method that applied the attenuation of each layer as a reference combined with a method that corrects based on the attenuation of the analysis position were applied. It was found that the method using the average attenuation of each layer is the most effective. This correction method is well adapted to the extended depth of field provided by an annular array.


Author(s):  
Weiran Pang ◽  
Yongjun Wang ◽  
Lili Guo ◽  
Bo Wang ◽  
Puxiang Lai ◽  
...  

Existing acoustic-resolution photoacoustic/ultrasonic endoscopy (PA/USE) generally employs a point-focused transducer for ultrasound detection, which is only sensitive in its focal region, thus the lateral resolution and sensitivity drop dramatically when the targets move far from its focus. Even if a dynamic focusing algorithm is applied, the sensitivity out of the transducer focus is still much lower than that in the focus in ultrasonic imaging mode. In this work, we propose an acoustic-resolution PA/USE with a line-focused transducer to realize automatic focusing for the first time. In comparison to a point-focused transducer, the line-focused transducer emits a more uniform sound field, causing the original signal intensity and signal-to-noise ratio (SNR) of the front and rear targets to be closer in the radial direction, which is beneficial for improving target signal uniformity in ultrasonic imaging. Simultaneously, we improved the resolution of the defocus area by modifying a prior work of back-projection (BP) reconstruction algorithm typically used in point-focused transducer based PAE and applying it to line-focused PA/USE. This combined approach may significantly enhance the depth of field of ultrasonic imaging and the resolution of the defocus zone in PA/US imaging, compared to the conventional method. Sufficient numerical simulations and phantom experiments were performed to verify this method. The results show that our method can effectively improve the lateral resolution in the image’s defocused region to achieve automatic focusing and perfectly solve the defect of the target signal difference in the far-focus region in ultrasonic imaging, while also enhancing the image SNR and contrast. The proposed method in this paper lays foundations for the realization of photoacoustic/ultrasonic combined endoscopy with enhanced lateral resolution and depth of field, which can potentially benefit a many of biomedical applications.


2021 ◽  
Vol 2021 ◽  
pp. 1-7
Author(s):  
Ruo-Peng Zheng ◽  
Shu-Bin Liu ◽  
Lei Li

Due to the limitation of numerical aperture (NA) in a microscope, it is very difficult to obtain a clear image of the specimen with a large depth of field (DOF). We propose a deep learning network model to simultaneously improve the imaging resolution and DOF of optical microscopes. The proposed M-Deblurgan consists of three parts: (i) a deblurring module equipped with an encoder-decoder network for feature extraction, (ii) an optimal approximation module to reduce the error propagation between the two tasks, and (iii) an SR module to super-resolve the image from the output of the optimal approximation module. The experimental results show that the proposed network model reaches the optimal result. The peak signal-to-noise ratio (PSNR) of the method can reach 37.5326, and the structural similarity (SSIM) can reach 0.9551 in the experimental dataset. The method can also be used in other potential applications, such as microscopes, mobile cameras, and telescopes.


Micromachines ◽  
2021 ◽  
Vol 13 (1) ◽  
pp. 17
Author(s):  
Jorabar Singh Nirwan ◽  
Shan Lou ◽  
Saqib Hussain ◽  
Muhammad Nauman ◽  
Tariq Hussain ◽  
...  

Electrically tunable lenses (ETLs) are those with the ability to alter their optical power in response to an electric signal. This feature allows such systems to not only image the areas of interest but also obtain spatial depth perception (depth of field, DOF). The aim of the present study was to develop an ETL-based imaging system for quantitative surface analysis. Firstly, the system was calibrated to achieve high depth resolution, warranting the accurate measurement of the depth and to account for and correct any influences from external factors on the ETL. This was completed using the Tenengrad operator which effectively identified the plane of best focus as demonstrated by the linear relationship between the control current applied to the ETL and the height at which the optical system focuses. The system was then employed to measure amplitude, spatial, hybrid, and volume surface texture parameters of a model material (pharmaceutical dosage form) which were validated against the parameters obtained using a previously validated surface texture analysis technique, optical profilometry. There were no statistically significant differences between the surface texture parameters measured by the techniques, highlighting the potential application of ETL-based imaging systems as an easily adaptable and low-cost alternative surface texture analysis technique to conventional microscopy techniques.


2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Zhu Weixin ◽  
Kong Dejun

Abstract NiMo-5%TiC, NiMo-15%TiC, and NiMo-25%TiC coatings were prepared on GCr15 steel by laser cladding (LC). The microstructure and the phases of the obtained coatings were analyzed using ultra-depth-of-field microscopy (UDFM) and X-ray diffraction (XRD), respectively. A ball-on-disk wear test was used to analyze the friction-wear performance of the substrate and the NiMo-TiC coatings under grease-lubrication condition. The results show that the grain shape of NiMo-TiC coatings is dendritic. The wear resistance of NiMo-TiC coatings is improved by the addition of TiC, and the depths of the worn tracks on the substrate and on the NiMo-5%TiC, NiMo-15%TiC, and NiMo-25%TiC coatings are 4.183 μm, 2.164 μm, 1.882 μm, and 1.246 μm, respectively, and the corresponding wear rates are 72.25 μm3/s/N, 32.00 μm3/s/N, 18.10 μm3/s/N, and 7.99 μm3/s/N, respectively; this shows that the NiMo-25%TiC coating has the highest wear resistance among the three kinds of coatings. The wear mechanism of NiMo-TiC coatings is abrasive wear, and the addition of TiC plays a role in resisting wear during the friction process.


Author(s):  
Jonathan Mark Mark Hallam ◽  
Thomas Kissinger ◽  
Thomas Charrett ◽  
Ralph P Tatam

Abstract In this work a range resolved interferometry (RRI) instrument for absolute distance measurements is integrated into a wire + arc additive manufacturing (WAAM) system to provide in-process monitoring of layer height, and prospects for volume and profile monitoring are discussed. Interferometry as a coherent optical technique offers a straightforward in-process measurement even in the harsh welding environment, as compared to non-coherent techniques based either on laser profiling or camera vision systems. RRI can be accomplished at significantly lower cost, and with higher depth of field (up to 10s of cm) than existing optical coherence tomography based weld monitoring. In this experiment titanium feedstock was used to create a 150mm long, 13.5mm high weld-wall comprised of 11 welded layers. The RRI in-process measurements are in very good agreement with both mid-process, on-machine micrometer measurements taken by hand after each weld, and post-process laser scanning measurements of the completed wall. The high depth of field allows direct referencing of the layer height measurements to the build plate making the measurement independent of the motion system and build plate bending, considerably lowering uncertainties. This, together with the capability for cost-effective in-process measurements in harsh environments, should make the proposed approach very interesting for routine use in WAAM systems.


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