James S. Goddard

Vision system for on-loom fabric inspection

This paper describes a vision-based fabric inspection system that accomplishes on-loom inspection of the fabric under construction with 100% coverage. The inspection system, which offers a scalable open architecture, can be manufactured at relatively low cost using off-the-shelf components. While synchronized to the motion of the loom, the developed system first acquires very high-quality vibration-free images of the fabric using either front or backlighting. Then, the acquired images are subjected to a novel defect segmentation algorithm, which is based on the concepts of wavelet transform, image fusion and the correlation dimension. The essence of this segmentation algorithm is the localization of those events (i.e., defects) in the input images that disrupt the global homogeneity of the background texture. The efficacy of this algorithm, as well as the overall inspection system, has been tested thoroughly under realistic conditions. The system was used to acquire and to analyze more than 3700 images of fabrics that were constructed with two different types of yarn. In each case, the performance of the system was evaluated as an operator introduced defects from 26 categories into the weaving process. The overall detection rate of the presented approach was found to be 89% with a localization accuracy of 0.2 in (i.e., the minimum defect size) and a false alarm rate of 2.5%.

Method for the measurement of the modulation transfer function of sampled imaging systems from bar-target patterns

A rigorous and simple method for the determination of the modulation transfer function (MTF) of a sampled imaging system is presented. One calculates the MTF by imaging bar patterns and calculating the reduction in amplitude of the fundamental frequency components. The optimal set of bar-pattern frequencies that reduce errors from aliased frequency components is derived. Theoretical and experimental data are presented.

A restraint-free small animal SPECT imaging system with motion tracking

We report on an approach toward the development of a high-resolution single photon emission computed tomography (SPECT) system to image the biodistribution of radiolabeled tracers such as Tc-99m and I-125 in unrestrained/unanesthetized mice. An infrared (IR)-based position tracking apparatus has been developed and integrated into a SPECT gantry. The tracking system is designed to measure the spatial position of a mouses head at a rate of 10-15 frames per second with submillimeter accuracy. The high-resolution, gamma imaging detectors are based on pixellated NaI(Tl) crystal scintillator arrays, position-sensitive photomultiplier tubes, and novel readout circuitry requiring fewer analog-digital converter (ADC) channels while retaining high spatial resolution. Two SPECT gamma camera detector heads based upon position-sensitive photomultiplier tubes have been built and installed onto the gantry. The IR landmark-based pose measurement and tracking system is under development to provide animal position data during a SPECT scan. The animal position and orientation data acquired by the tracking system will be used for motion correction during the tomographic image reconstruction.

Real-time landmark-based unrestrained animal tracking system for motion-corrected PET/SPECT imaging

Oak Ridge National Laboratory (ORNL) and Jefferson Lab and are collaborating to develop a new high-resolution single photon emission tomography (SPECT) instrument to image unrestrained laboratory animals. This technology development will allow functional imaging studies to be performed on the animals without the use of anesthetic agents. This technology development could have eventual clinical applications for performing functional imaging studies on patients that cannot remain still (Parkinsons patients, Alzheimers patients, small children, etc.) during a PET or SPECT scan. A key component of this new device is the position tracking apparatus. The tracking apparatus is an integral part of the gantry and designed to measure the spatial position of the animal at a rate of 10-15 frames per second with sub-millimeter accuracy. Initial work focuses on brain studies where anesthetic agents or physical restraint can significantly impact physiologic processes.

Direct to digital holography for semiconductor wafer defect detection and review

A method for recording true holograms directly to a digital video medium in a single image has been invented. This technology makes the amplitude and phase for every pixel of the target object wave available. Since phase is proportional wavelength, this makes high-resolution metrology an implicit part of the holographic recording. Measurements of phase can be made to one hundredth or even one thousandth of a wavelength, so the technology is attractive for dining defects on semiconductor wafers, where feature sizes are now smaller than the wavelength of even deep UV light.

Development and testing of a restraint free small animal SPECT imaging system with infrared based motion tracking

The development and initial evaluation of a high-resolution single photon emission tomography (SPECT) based system to image the biodistribution of radiolabeled tracers such as Tc-99m and I-125 in unrestrained/un-anesthetized mice. An infrared (IR) based position tracking apparatus has been developed and integrated into a SPECT gantry. The tracking system is designed to measure the spatial position of a mouses head at a rate of 10-15 frames per second with sub-millimeter accuracy. The high resolution, gamma imaging detectors are based on pixelated NaI(Tl) crystal scintillator arrays, arrays of compact position-sensitive photomultiplier tubes and novel readout circuitry for lower device cost while retaining high spatial resolution. Two SPECT gamma camera detector heads based on a 4 /spl times/ 8 array of Hamamatsu R8520-C12 position sensitive photomultiplier tubes have been built and installed onto the gantry. The IR landmark-based pose measurement and tracking system is under development to provide animal position data during a SPECT scan. The animal position and orientation data acquired by the IR tracking system is used for motion correction during the tomographic image reconstruction.

Direct To Digital Holography For High Aspect Ratio Inspection of Semiconductor Wafers

Direct to Digital Holography (DDH) has been developed as a semiconductor wafer inspection tool and in particular as a tool for seeing defects in high aspect ratio (HAR) structures on semiconductor wafers and also for seeing partial‐height defects. While the tool works very well for general wafer inspection, it has unusual capabilities for high aspect ratio inspection (HARI) and for detecting thin residual film defects (partial height defects). Inspection of HAR structures is rated as one of the highest unmet priorities of the member companies of International SEMATECH, and finding residual thin film defects (in some cases called “stringers”) is also a very difficult challenge. The capabilities that make DDH unusually sensitive include: 1) the capture of the whole wave—both the classical amplitude captured by traditional optical systems, and the phase of the wave, with phase potentially measured to ∼1/1000’th of a wavelength or ∼2 to 3 Angstroms for a deep ultra‐violet (DUV) laser; 2) heterodyne detection—...

Online optical measurement and monitoring of yarn density in woven fabrics

This paper describes a vision-based system that monitors the yarn density of woven fabrics on-line. The system is described in terms of its two principal modules, namely, the image acquisition and the image analysis subsystems. The image acquisition subsystem is implemented with standard components on a low-cost personal computer platform. These components consist of a line-scan camera, a DSP-based image acquisition and processing card, and a host personal computer. The image acquisition process is controlled by a software module that runs on the DSP board and accumulates a 2D image suitable for the density measurement algorithm. The image analysis subsystem, which also runs on the DSP board, implements a novel, yet straightforward, algorithm that utilizes the discrete Fourier transform for monitoring the yarn density of the fabrics from the acquired images. In this algorithm, the Fourier spectrum of the images is covered by contiguous, concentric annular regions that have a prespecified width. THe spectrum values within each annular region are summed, normalized, and subsequently used to produce a 1D signature. Simple statistics of the obtained signatures are the basis for characterizing the fabric in terms of its yarn density. The described system is tested on seven fabrics with common properties but varying yarn densities and has shown to be accurate within 2 yarns per inch in either direction. It is also shown that the obtained accuracy, which is primarily a function of the image resolution, can be greatly improved.

Instrumentation Development of a SPECT-CT System to Image Awake Mice

We report on the instrumentation development of a SPECT-CT system being configured at Johns Hopkins University to image the bio distribution of radiopharmaceuticals in unrestrained, unanesthetized mice. The gantry is a custom built X-ray computed tomography system based on the Siemens MicroCAT II imaging system. The X-ray system is composed of an 80 kVp (max), 40W X-ray source and a 2048 times 3096-pixel detector (5-frames per second readout). The mouse will be anesthetized during the X-ray CT scan. SPECT imaging will be achieved using two low profile gamma cameras, 10 cm times 20 cm in size based on a 2times4 array of Hamamatsu H8500 (8times8 anode pads) flat panel position sensitive photomultiplier tubes (PSPMT). A Nal(Tl) scintillator array with 1.2 mm pitch is mounted to the PSPMT array. The front end readout electronics combine the anode outputs of the PSPMTs of the detector head. The data acquisition system is based on two CAEN 32 channel VME peak sensing analog-digital converter (ADC) modules per detector head to digitize the outputs. An infrared based animal position tracking system will be used to monitor the mouses head position during a SPECT scan via infrared illuminated markers attached to the mouses head. The mouse is confined in an infrared transparent burrow at the center of rotation of the gantry. The tracking system is able to track with sub-millimeter accuracy the mouses head position at 10-15 frames per second.

Real-time, high-accuracy 3D tracking of small animals for motion-corrected SPECT imaging

An optical landmark-based pose measurement and tracking system has been developed to provide 3D animal position data for a single photon emission computed tomography (SPECT) imaging system for non-anesthetized, unrestrained laboratory animals. The animal position and orientation data provides the opportunity for motion correction of the SPECT data. The tracking system employs infrared (IR) markers placed on the animals head along with strobed IR LEDs to illuminate the reflectors. A stereo CMOS camera system acquires images of the markers through a transparent enclosure. Software routines segment the markers, reject unwanted reflections, determine marker correspondence, and calculate the 3D pose of the animals head. Recent improvements have been made in this tracking system including enhanced pose measurement speed and accuracy, improved animal burrow design, and more effective camera positioning for enhanced animal viewing. Furthermore, new routines have been developed to calibrate the SPECT detector head positions relative to one another and to align the coordinate systems of the optical tracking cameras with the SPECT detectors. This alignment enables motion-corrected SPECT image reconstruction. Phantom experiments validate the accuracy of the tracking system to better than 0.1 mm accuracy, and live mouse tracking results demonstrate that reliable, accurate tracking measurements can be consistently achieved during the entire 360-degree SPECT image acquisition.