We report a new method for automated identification and measurement of primary particles within soot aggregates as well as the sizes of the aggregates and discuss its application to high-resolution transmission electr...
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We report a new method for automated identification and measurement of primary particles within soot aggregates as well as the sizes of the aggregates and discuss its application to high-resolution transmission electron microscope (TEM) images of the aggregates. The imageprocessing algorithm is based on an optimized Hough transform, applied to the external border of the aggregate. This achieves a significant data reduction by decomposing the particle border into fragments, which are assumed to be spheres in the present application, consistent with the known morphology of soot aggregates. Unlike traditional techniques, which are ultimately reliant on manual (human) measurement of a small sample of primary particles from a subset of aggregates, this method gives a direct measurement of the sizes of the aggregates and the size distributions of the primary particles of which they are composed. The current version of the algorithm allows processing of high-resolution TEM images by a conventional laptop computer at a rate of 1-2 ms per aggregate. The results were validated by comparison with manual imageprocessing, and excellent agreement was found. (C) 2012 Optical Society of America
This paper addresses the high-precision measurement of the distortion of a digital camera from photographs. Traditionally, this distortion is measured from photographs of a flat pattern that contains aligned elements....
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This paper addresses the high-precision measurement of the distortion of a digital camera from photographs. Traditionally, this distortion is measured from photographs of a flat pattern that contains aligned elements. Nevertheless, it is nearly impossible to fabricate a very flat pattern and to validate its flatness. This fact limits the attainable measurable precisions. In contrast, it is much easier to obtain physically very precise straight lines by tightly stretching good quality strings on a frame. Taking literally "plumb-line methods," we built a "calibration harp" instead of the classic flat patterns to obtain a high-precision measurement tool, demonstrably reaching 2 /100 pixel precisions. The harp is complemented with the algorithms computing automatically from harp photographs two different and complementary lens distortion measurements. The precision of the method is evaluated on images corrected by state-of-the-art distortion correction algorithms, and by popular software. Three applications are shown: first an objective and reliable measurement of the result of any distortion correction. Second, the harp permits us to control state-of-the art global camera calibration algorithms: it permits us to select the right distortion model, thus avoiding internal compensation errors inherent to these methods. Third, the method replaces manual procedures in other distortion correction methods, makes them fully automatic, and increases their reliability and precision. (c) 2012 Optical Society of America
Spot distortion caused by astigmatism effect in orthogonal cylindrical lenses is utilized to measure axial displacement with 30 nm resolution, strong noise immunity, and compact experiment setup. Axial displacement of...
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Spot distortion caused by astigmatism effect in orthogonal cylindrical lenses is utilized to measure axial displacement with 30 nm resolution, strong noise immunity, and compact experiment setup. Axial displacement of the sample surface is determined by four-quadrant difference processing of distorted laser spots' energy distribution images received by CCD. Four-quadrant difference processing results indicate an applicable measuring range of 5.6 mu m (cubic fitting r = 0.9988) with a highly linear range of 1.2 mu m (linear fitting r = 0.9996). Factors affecting measuring range and sensitivity are analyzed by theoretical deduction and numerical simulation. This technique has potential applications in drifting sample tracking and measurement in advanced microscopy. (c) 2012 Optical Society of America
Three-dimensional (3D) images of flame emission are reported using a single direction of optical access. A Cassegrain system was designed with narrow depth of field. images from this system are dominated by emission f...
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Three-dimensional (3D) images of flame emission are reported using a single direction of optical access. A Cassegrain system was designed with narrow depth of field. images from this system are dominated by emission from the focused object plane with defocused contributions from out-of-plane structures. Translation of one mirror in the system allows for scanning the object plane through the flame. images were taken at various depths to create a family of images. Reconstruction of the 3D flame structure was accomplished using a maximum entropy algorithm adapted for use with 3D imaging. Spatial resolution in the direction of imaging is examined using laminar flames with variable offset. (C) 2012 Optical Society of America
This paper presents the design of a multichannel imaging system where the different optical channels have a different angular resolution and field-of-view. Such an imaging system is able to resolve fine details in a s...
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This paper presents the design of a multichannel imaging system where the different optical channels have a different angular resolution and field-of-view. Such an imaging system is able to resolve fine details in a small region of interest through the channel that has the highest angular resolution (0.0096 degrees) while controlling the surrounding region through the channel that has the widest field-of-view (2 x 40 degrees). An interesting feature of such a multichannel, multiresolution imaging system is that various image processing algorithms can be applied at different segments of the image sensor. We have designed a three channel imaging system where each optical channel consists of four aspheric lens surfaces. These three imaging channels share a single image sensor with a resolution of 1440 x 960 and a 10 mu m pixel size. All imaging channels have diffraction-limited performance ensuring good overall image quality. (C) 2012 Optical Society of America
We describe an adaptive coded-aperture imager operating in the midwave IR. This consists of a coded-aperture mask, a set of optics, and a 4k x 4k focal plane array (FPA). This system can produce images with a resoluti...
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We describe an adaptive coded-aperture imager operating in the midwave IR. This consists of a coded-aperture mask, a set of optics, and a 4k x 4k focal plane array (FPA). This system can produce images with a resolution better than the detector pixel limit by combining multiple frames of data recorded with different coding. This superresolution capability has been demonstrated both in the laboratory and with targets placed outside, the highest resolution being one-half of the FPA pixel pitch. (C) 2012 Optical Society of America
Large-scale and cost-effective manufacturing of ceramic micro devices based on tape stacking requires the development of inspection systems to perform high-resolution in-process quality control of embedded manufacture...
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Large-scale and cost-effective manufacturing of ceramic micro devices based on tape stacking requires the development of inspection systems to perform high-resolution in-process quality control of embedded manufactured cavities, metal structures and defects. With an optical coherence tomography (OCT) system operating at 1.3 mu m and a dedicated automated line segmentation algorithm, layer thicknesses can be measured and laser-machined channels can be verified in alumina ceramics embedded at around 100 mu m depth. Monte Carlo simulations are employed to analyze the abilities of OCT in imaging of the embedded channels. The light scattering parameters required as input data for simulations are evaluated from the integrating sphere measurements of collimated and diffuse transmittance spectra using a reconstruction algorithm based on refined diffusion approximation approach. (C)2012 Optical Society of America
Speckle velocimetry is investigated as a means of determining odometry data with potential for application on autonomous robotic vehicles. The technique described here relies on the integration of translation measurem...
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Speckle velocimetry is investigated as a means of determining odometry data with potential for application on autonomous robotic vehicles. The technique described here relies on the integration of translation measurements made by normalized cross-correlation of speckle patterns to determine the change in position over time. The use of objective (non-imaged) speckle offers a number of advantages over subjective (imaged) speckle, such as a reduction in the number of optical components, reduced modulation of speckles at the edges of the image, and improved light efficiency. The influence of the source/ detector configuration on the speckle translation to vehicle translation scaling factor for objective speckle is investigated using a computer model and verified experimentally. Experimental measurements are presented at velocities up to 80 mm s(-1) which show accuracy better than 0.4%. (C) 2012 Optical Society of America
Conventional intensity imaging through turbid media suffers from rapid loss of image contrast due to light scattering from particles or random variations of refractive index. This paper features the development of an ...
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Conventional intensity imaging through turbid media suffers from rapid loss of image contrast due to light scattering from particles or random variations of refractive index. This paper features the development of an active imaging, snapshot, system design and postprocessingalgorithms that differentiate between radiation that scatters or reflects from remote, obscured objects and the radiation from the scattering media itself through a combination of polarization difference imaging, channel blurring, and Fourier spatial filtering. The produced sensor acquires and processes image data in real time, yielding improved image contrasts by factors of 10 or greater for dense water vapor obscurants. (C) 2012 Optical Society of America
Millimeter wave (MMW) imaging is finding rapid adoption in security applications such as concealed object detection under clothing. A passive MMW imaging system can operate as a stand-off type sensor that scans people...
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Millimeter wave (MMW) imaging is finding rapid adoption in security applications such as concealed object detection under clothing. A passive MMW imaging system can operate as a stand-off type sensor that scans people in both indoors and outdoors. However, the imaging system often suffers from the diffraction limit and the low signal level. Therefore, suitable intelligent image processing algorithms would be required for automatic detection and recognition of the concealed objects. This paper proposes real-time outdoor concealed-object detection and recognition with a radiometric imaging system. The concealed object region is extracted by the multi-level segmentation. A novel approach is proposed to measure similarity between two binary images. Principal component analysis (PCA) regularizes the shape in terms of translation and rotation. A geometric-based feature vector is composed of shape descriptors, which can achieve scale and orientation-invariant and distortion-tolerant property. Class is decided by minimum Euclidean distance between normalized feature vectors. Experiments confirm that the proposed methods provide fast and reliable recognition of the concealed object carried by a moving human subject. (C) 2012 Optical Society of America
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