Yufu Qu

Yufu Qu
Beihang University (BUAA) | BUAA · Department of instrument science and opto-electrical engineering

Doctor of Philosophy

About

42
Publications
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245
Citations

Publications

Publications (42)
Article
Full-text available
Through-focus scanning optical microscopy (TSOM) is one of the recommended measurement methods in semiconductor manufacturing industry in recent years because of its rapid and nondestructive properties. As a computational imaging method, TSOM takes full advantage of the information from defocused images rather than only concentrating on focused ima...
Article
Through-focus scanning optical microscopy (TSOM) is a model-based optical metrology for nano-scaled geometries with abilities of high efficiency, low cost, and non-destruction. The state-of-the-art studies on TSOM have been devoted to improving accuracies of single variable measurements or multiple variable measurements in limited degree of freedom...
Article
Through‐focus scanning optical microscopy (TSOM) is a model‐based nanoscale metrology technique which combines conventional bright‐field microscopy and the relevant numerical simulations. A TSOM image is generated after through‐focus scanning and data processing. However, the mechanical vibration and optical noise introduced into the TSOM image dur...
Article
Through‐focus scanning optical microscopy (TSOM) is an economical, non‐contact and nondestructive method for rapid measurement of three‐dimensional nanostructures. There are two methods using TSOM image to measure the dimensions of one sample, including the library‐matching method and the machine‐learning regression method. The first has the defect...
Article
Full-text available
Through-focus scanning optical microscopy (TSOM) is an economical and nondestructive method for measuring three-dimensional nanostructures. After obtaining a TSOM image, a library-matching method is typically used to interpret optical intensity information and determine the dimensions of a measurement target. To further improve dimensional measurem...
Article
Full-text available
To avoid the need for a mask and polarization-adjusting devices, and to solve the problem of low fringe contrast caused by the reflected light along with zero-order diffraction beam, this paper presents an illumination method using three nonzero-order diffraction beams in liquid crystal on silicon (LCOS)-based structured illumination microscopy. He...
Article
Full-text available
High‐throughput through‐focus scanning optical microscopy (TSOM) involves defocusing along the optical axis and capturing a series of defocus images and is useful in optical nanoscale measurement. However, TSOM is usually affected by its optical and mechanical noises. In this study, the issue of sensitivity and application in three‐dimensional (3D)...
Article
Traditional methods of stripe noise removal based on space domain or transformation domain generally cannot handle the case where the noise is extremely sparse. To solve this problem, we propose a novel approach to accurately detect and remove the stripe noise by analyzing the directional and structural information of the stripe noise. First, we bu...
Article
Full-text available
Inserting an electrically tunable lens (ETL), such as liquid lens or tunable acoustic gradient lens, into a microscope can enable fast axial scanning, autofocusing, and extended depth of field. However, placing the ETL at different positions has different influences on image quality. Specially, in a wide‐field microscope for measurement, the magnif...
Article
Full-text available
Unlike the optical information taken from a single in-focus image of general optical microscopy, through-focus scanning optical microscopy (TSOM) involves scanning a target through the focus and capturing of a series of images. These images can be used to conduct three-dimensional inspection and metrology with nanometer-scale lateral and vertical s...
Article
Monocular rotational microscopes suffer from shallow depth of field and reduced field of view. Consequently, we propose monocular wide‐field optical microscopy with extended depth of field to enable accurate 3D measurements of micro‐objects. We use a liquid lens and a 4f system to extend the system's depth of field and two additional rotational ref...
Article
Due to the large slope and complex geometry, it is difficult to measure the three‐dimensional parameters of cutting tools and drill bits by using general optical measurement method. A method that combines the multiview rotation scanning and nonmechanical focus variation by using a liquid lens is proposed in this paper. Firstly, the workpiece is rot...
Article
Full-text available
In order to reconstruct three-dimensional (3D) structures from an image sequence captured by unmanned aerial vehicles' camera (UAVs) and improve the processing speed, we propose a rapid 3D reconstruction method that is based on an image queue, considering the continuity and relevance of UAV camera images. The proposed approach first compresses the...
Article
Full-text available
Photographic images taken in foggy or hazy weather (hazy images) exhibit poor visibility and detail because of scattering and attenuation of light caused by suspended particles, and therefore, image dehazing has attracted considerable research attention. The current polarization-based dehazing algorithms strongly rely on the presence of a “sky area...
Article
Full-text available
High accuracy target recognition and tracking systems using a single sensor or a passive multisensor set are susceptible to external interferences and exhibit environmental dependencies. These difficulties stem mainly from limitations to the available imaging frequency bands, and a general lack of coherent diversity of the available target-related...
Article
Huge data volumes and redundant information are common problems in the field of hyperspectral target recognition. In this study, we propose a method to ensure the accuracy of target recognition while reducing the amount of data, where the effective bands in the hyperspectral data are selected for which the third-order derivative spectrum approaches...
Article
For the design of a passive autofocusing (AF) system for optical microscopes, many time-consuming and tedious experiments have been performed to determine and design a better focus criterion function, owing to the sample-dependence of this function. To accelerate the development of the AF systems in optical microscopes and to increase AF speed as w...
Conference Paper
Due to the small field of view and shallow depth of field, the microscope could only capture 2D images of the object. In order to observe the three-dimensional structure of the micro object, a microscopy images reconstruction algorithm based on an improved patch-based multi-view stereo (PMVS) algorithm is proposed. The new algorithm improves PMVS f...
Article
Full-text available
To obtain the accurate integral PSF of an extended depth of field (EDOF) microscope based on liquid tunable lens and volumetric sampling (VS) method, a method based on statistic and inverse filtering using quantum dot fluorescence nanosphere as a point source is proposed in this paper. First, a number of raw quantum dot images were captured separat...
Conference Paper
To avoid “stair-casing effect” in the disparity map when dealing with slant plane, curved surface and weak texture region, an improved fast dense stereo matching algorithm based on disparity plane estimation is proposed. First, a set of support points are extracted from the edge of the original matching images and the description images. Second, De...
Article
The axial imaging range of optical microscopy is restricted by its fixed working plane and limited depth of field. In this paper, the axial capabilities of an off-the-shelf microscope is improved by inserting a liquid lens, which can be controlled by a driving electrical voltage, into the optical path of the microscope. First, the numerical formula...
Article
Full-text available
A nozzle angle measurement system based on monocular vision is proposed to achieve high-speed and non-contact angle measurement of rocket engine nozzle. The measurement system consists of two illumination sources, a lens, a target board with spots, a high-speed camera, an image acquisition card and a PC. A target board with spots was fixed on the e...
Article
Full-text available
The authors present a local stereo matching algorithm whose performance is insensitive to changes in radiometric conditions between the input images. First, a prior on the disparities is built by combining the DAISY descriptor and Census filtering. Then, a Census-based cost aggregation with a self-adaptive window is performed. Finally, the maximum...
Article
Parameter adjustment of the transmitted light source yields a good-quality image for video measurement microscopy. However, a disadvantage is that the measured size of the objects changes simultaneously while the parameters of the transmitted light source are adjusted, which directly affects the measurement accuracy adversely. Furthermore, the vari...
Article
Conventional optical imaging systems are limited by a fundamental trade-off between the depth of field (DOF) and signal-to-noise ratio. Apart from a large DOF, a constant magnification within a certain depth range is particularly essential for visual measurement systems. In this paper, we present a novel visual measurement system with extended DOF...
Article
In this paper, we first introduce the concept of the depth of field (DOF) in machine vision systems, which serves as a basic building block for our study. Then, related work on the generalization of the fundamental methods and current status with regard to extending the DOF is presented, followed by a detailed analysis of the principles and perform...
Article
Autofocusing (AF) criterion functions are critical to the performance of a passive autofocusing system in automatic video microscopy. Most of the autofocusing criterion functions proposed are dependent on the imaging system and image captured by the objective being focused or ranged. This dependence destabilizes the performance of the system when t...
Article
To obtain high speed and accuracy, passive autofocusing system and two-stage searching strategy have been widely applied in microscopy. The kernel of the passive autofocusing system is the selection of the focus criterion functions, which will significantly affect the efficiency and accuracy of the autofocusing system. In order to help choose the b...
Article
Full-text available
For automating the remote voice detection using a laser Doppler vibrometer (LDV), we integrate a pan-tilt-zoom (PTZ) camera, a mirror, and a pan-tilt unit (PTU) with the LDV to form a multimodal sensing system. With the assistance of vision and active control components, the LDV can automatically select the best reflective surfaces, point the laser...
Conference Paper
Full-text available
Laser Doppler Vibrometers (LDVs) have been widely applied for detecting vibrations in applications such as mechanics, bridge inspection, biometrics, as well as long-range surveillance in which acoustic signatures can be obtained at a large distance. However, in both industrial and scientific applications, the LDVs are manually controlled in surface...
Conference Paper
Full-text available
Both panoramic and multimodal imaging are becoming more and more desirable in applications such as wide area surveillance, robotics, mapping and entertainment. In this paper, we build a precise rotating platform to generate co-registered multimodal and multiview 3D panoramic images. The platform consists of a pair of color and thermal cameras that...
Article
Full-text available
To improve the performance and the efficiency of Laser Doppler Vibrometers (LDVs) for long-range hearing, we design an active multimodal sensing platform that integrates a Pan-Tilt-Zoom (PTZ) camera, a mirror and a Pan-Tilt-Unit (PTU) to the LDV. With the assistance of the vision and active control components, the LDV can automatically select the b...
Article
Full-text available
To address the challenges of noncooperative, large-distance human signature detection, we present a novel multimodal remote audio/video acquisition system. The system mainly consists of a laser Doppler virbometer (LDV) and a pan-tilt-zoom (PTZ) camera. The LDV is a unique remote hearing sensor that uses the principle of laser interferometry. Howeve...
Article
A target characterization sensor is proposed, which can obtain a three-dimensional (3D) structure, hyperspectrum, and complete Stokes polarization characters corresponding to the target pixel scale from the same viewpoint. This avoids matching information processes and improves target characterization precision. The target characterization sensor i...
Article
A new acoustic grating fringe projector (AGFP) was developed for high-speed and high-precision 3D measurement. A new acoustic grating fringe projection theory is also proposed to describe the optical system. The AGFP instrument can adjust the spatial phase and period of fringes with unprecedented speed and accuracy. Using rf power proportional-inte...
Conference Paper
The optical wavefront becomes aberrated when the object optical wavefront propagates through index-of-refractionvariant, turbulent fluid. This paper related optical wavefront distortions to the fluid-mechanical behaviors. It deduces Interfacial-Refraction-Index-Thickness (IRIT) approach on the basis of eikonal equation. It simulated turbulent refra...
Conference Paper
Under high magnification of the micro-vision systems, the original metal texture appears in the form of bright spots with different shapes and different sizes and mixes with the real flaws such as maculae, pockmarks, and corrosions. The background of the image is complex while the image brightness is non-uniform due to the spherical reflection. It...
Article
Full-text available
The selection of an image quality assessment criterion plays a key role when an illuminant of autoregulative intensity is designed for a vision measurement system. In this work eight image quality assessment functions were compared and analyzed with adjustment of the illumination intensity from weak to strong. Four different workpieces, each repres...
Article
Full-text available
A 3D coordinate measurement method of free-form surface was designed, which combines 3D coordinate measuring machine with single camera. The coordinate measuring machine drives the camera to capture the free-form surface image sequentially and form the image volume. Then the focused image surface (FIS) of the free-form surface is determined by sear...
Article
The precision of auto-focus system is affected directly by the sensitivity of focus criteria function. In many researches about performance of focus criteria functions, the sensitivity of each different function is commonly compared, but ignoring that the sensitivity of focus criteria function is not only connected with the function itself but also...
Conference Paper
This paper presents a novel methodology that integrates a vision system and a coordinate measuring machine for rapid coordinate metrology. Rapid acquisition of coordinate data from parts having tiny dimension, complex geometry and soft or fragile material has many applications. Typical examples include Large Scale Integrated circuit, glass or plast...

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Project
computational