727 research outputs found
An update of commercial infrared sensing and imaging instruments
A classification of infrared sensing instruments by type and application, listing commercially available instruments, from single point thermal probes to on-line control sensors, to high speed, high resolution imaging systems is given. A review of performance specifications follows, along with a discussion of typical thermographic display approaches utilized by various imager manufacturers. An update report on new instruments, new display techniques and newly introduced features of existing instruments is given
Medical ultrasonic tomographic system
An electro-mechanical scanning assembly was designed and fabricated for the purpose of generating an ultrasound tomogram. A low cost modality was demonstrated in which analog instrumentation methods formed a tomogram on photographic film. Successful tomogram reconstructions were obtained on in vitro test objects by using the attenuation of the fist path ultrasound signal as it passed through the test object. The nearly half century tomographic methods of X-ray analysis were verified as being useful for ultrasound imaging
Looking at the unborn: historical aspects of obstetric ultrasound
The obstetric ultrasound scanner had its major origins in a programme of research undertaken in Glasgow in the 1950s and 1960s, under the leadership of the obstetrician, Professor Ian Donald. Donald’s work was characterized by a remarkable series of collaborations between engineers and clinicians, many of whom took part in this Witness Seminar to consider the early history of ultrasound imaging, its technical development and significant clinical applications in the diagnosis of fetal abnormalities. Technical and engineering developments of the scanner were discussed and it was practical demonstrations of the early scanners that gradually convinced the majority of obstetricians to invest time and training in this new technology. Participants include: Mr Usama Abdulla, Mr Thomas Brown, Professor Dugald Cameron, Professor Stuart Campbell, Mr John Fleming, Professor John MacVicar, Professor Peter Wells and Dr James Willocks. Introduction by E M Tansey, v, 80pp. 15 illustrations, glossary, subject and name index
Looking at the Unborn: Historical aspects of obstetric ultrasound
Edited trascript of a Witness Seminar held at the Wellcome Institute for the History of Medicine,in London, on 10 March 1998. First published by the Wellcome Trust, 2000. ©The Trustee of the Wellcome Trust, London, 2000. All volumes are freely available online at: www.history.qmul.ac.uk/research/modbiomed/wellcome_witnesses/Annotated and edited transcript of a Witness Seminar held on 10 March 1998. Introduction by E M Tansey.Annotated and edited transcript of a Witness Seminar held on 10 March 1998. Introduction by E M Tansey.Annotated and edited transcript of a Witness Seminar held on 10 March 1998. Introduction by E M Tansey.Annotated and edited transcript of a Witness Seminar held on 10 March 1998. Introduction by E M Tansey.The obstetric ultrasound scanner had its major origins in a programme of research undertaken in Glasgow in the 1950s and 1960s, under the leadership of the obstetrician, Professor Ian Donald. Donald’s work was characterized by a remarkable series of collaborations between engineers and clinicians, many of whom took part in this Witness Seminar to consider the early history of ultrasound imaging, its technical development and significant clinical applications in the diagnosis of fetal abnormalities. Technical and engineering developments of the scanner were discussed and it was practical demonstrations of the early scanners that gradually convinced the majority of obstetricians to invest time and training in this new technology. Participants include: Mr Usama Abdulla, Mr Thomas Brown, Professor Dugald Cameron, Professor Stuart Campbell, Mr John Fleming, Professor John MacVicar, Professor Peter Wells and Dr James Willocks. Tansey E M, Christie D A. (eds) (2000) Looking at the unborn: Historical aspects of obstetric ultrasound, Wellcome Witnesses to Twentieth Century Medicine, vol. 5. London: The Wellcome Trust.The Wellcome Trust is a registered charity, no. 210183
A study of the accuracy of reproduction of measured photography: A method to equate the tonal range of the color transparency to the tonal of the photomechanical reproduction
The density range of a color transparency greatly exceeds the density range capacity of reproductions with ink on paper. It is therfore necessary to perform tone compression. Traditionally, tone compression is accomplished by the color separator and involves subjective decisions without input from the photographer. Tone reproduction of the final image is a result of image manipulation by different people in production who are not in communication with each other. Consequently, image quality may suffer and important image detail may be lost as a result of improper estimates
Using measured photography to obtain optimal results from CCD Color Scanners
With the advent of desktop color scanners in the electronic prepress production environment, quality in color separations from transmissive originals has become erratic. The cause of this fluctuation is, in part, due to the transition from PMT to CCD-based scanning technology. Whereas, PMT scanners tend to have a broad dynamic range, that of CCD scanners is more limited. This characteristic adversely affects the quality of color separations by causing additional tone compression. An original transparency typically has a shadow density of 3.00 and a diffused highlight density of 0.30 for an overall density range of 2.70. On a four-color heatset web press with coated stock, the maximum reproducible tonal range corresponds to a density of 1.80. The difference in density of 0.90 between the original and the press sheet is unable to fit through the printing window unless it undergoes considerable tone compression. This project was based on two hypotheses. The first was that the lower the tonal range of a transmissive original the more readily lower-midtone-to-shadow tonality could be retained in the separations produced by a CCD scanner and related equipment. The second was that exposure latitude in the separations would decrease with increasing tonal range. The first stage of production was to produce twelve test transparencies by photograph ing a still life set to four tonal ranges: 3.5, 4.5, 5.5, and 6.5 f/stops. Within each range, three images were selected to represent normal exposure, 1/2 f/stop overexposure, and 1/2 f/stop underexposure. Comparison of halftone proofs, made from separations of the normallyexposed transparencies, were later used for the first hypothesis. Proofs from the 1/2 f/stop over- and 1/2 f/stop underexposures were compared with the normal exposures to test the second hypothesis. vm The twelve test transparencies were first scanned on the Dainippon Screen SG-608 to produce a set of best-of-kind reference separations and halftone proofs. Next, the trans parencies were scanned on two midrange 12-bit CCD scanners, one a Pixelcraft CIS 4520RS, the other an Agfa Horizon. Separations for both were produced with Color Access 1.3.3 software on a Macintosh Quadra 700 computer, linked to an Agfa SelectSet 5000 image-setter via an Agfa 5000PS Star Plus RIP. The image files were placed in an 8 1/2 X 11 QuarkXPress page with a 20% gray surround prior to output. Halftone proofs were produced with the Fuji Color Art proofing system, then viewed under 5000 Kelvin lighting. Three methods were used for comparison: visual evaluation by the author, densitometric measurement, and evaluation by 32 independent judges. Only proofs from the two CCD scanners were shown to the judges. Proofs from the SG-608, of noticeably higher quality, were used for reference. The four proofs from separations produced by normally-exposed originals were used to examine the first hypothesis. Two groups of proofs, one for each scanner, were ranked by the judges according to best-to-worst rendition of lower-midtone-to-shadow detail. The rank ings for both groups placed the 3.5 f/stop tonal ranges first, 4.5 f/stop second, 5.5 f/stop third, and 6.5 f/stop fourth. Visual evaluation by the author ranked the proofs in the same order, establishing a 100% correlation. Increases in density range were also expected to follow the 3.5 to 6.5 f/stop ranking. But actual measurements showed increases in density to 4.5 f/stops, then a pronounced drop of 0.25 or greater for the 5.5 and 6.5 f/stop ranges. This demonstated that the higher tonal ranges exceeded the capacity of the CCDs to make a full response, indicating that limited dynamic range was causing abrupt increases in tone compression. To determine the validity of the second hypothesis, the judges examined two groups of twelve proofs each, corresponding to the separations for normal, 1/2 f/stop over- and 1/2 f/stop underexposed originals within each of the four tonal ranges. For the Agfa Horizon, the rankings were 3.5 f/stop tonal range first, 4.5 f/stop second, 5.5 f/stop third, and 6.5 f/stop fourth. With the Pixelcraft CIS 4520RS, the rankings were 3.5 f/stop first, 6.5 f/stop second, 5.5 f/stop third, and 6.5 f/stop fourth. The misranking of the 6.5 f/stop range in second place indicated the difficulty the judges experienced in distinguishing between higher tonal ranges due to the increasing effects of tone compression. Again, densitometric measurements did not support the rank ings of the judges or the author because the densitometer could not distinguish between small tonal range differences due to good exposure latitude and those differences due to blocked shadow tonality resulting from tone compression. A procedure was devised for mathematical assessment of tonal range differences. Using the change in density between adjacent tonal ranges, a value was derived which could be expressed as a fraction of the inital 1 f/stop difference between ranges ( 1 f/stop = 0.30 den sity units). For example, the 3.5 f/stop normal exposure for the Agfa Horizon had a tonal range of 1.73 and the 4.5 f/stop normal exposure had a tonal range of 2.02. The change from 3.5 to 4.5 f/stops is +0.29. Expressed as a percentage, 0.29 -0.30 = 97%. This value showed that the scanner made a nearly complete response in translating tonal range differences in the original transparency to tonal range differences in the separations. Further refinement of these calculations is needed to reflect differences in gamma and tone compression between the original transparencies and the halftone proofs. The findings of this study demonstrate that optimal results from a CCD or PMT scan ner can only be obtained if the tonal range of the original scene is less than 4.5 f/stops. When the 4.5 f/stop range was exceeded, the CCD scanners responded with an immediate deterioration of lower-midtone-to-shadow tonality. In comparison, PMT scanner displayed a more gradual degradation of lower-midtone-to-shadow tonality, in keeping with its greater dynamic range
Forest and Range Inventory and Mapping
The state of the art in remote sensing for forest and range inventories and mapping has been discussed. There remains a long way to go before some of these techniques can be used on an operational basis. By the time that the Earth Resources Technology Satellite and Skylab space missions are flown, it should be possible to tell what kind and what quality of information can be extracted from remote sensors and how it can be used for surveys of forest and range resources
The usefulness of Skylab/EREP S-190 and S-192 imagery in multistage forest surveys
The author has identified the following significant results. The RMSE of point location achieved with the annotation system on S190A imagery was 100 m and 90 m in the x and y direction, respectively. Potential gains in sampling precision attributable to space derived imagery ranged from 4.9 to 43.3 percent depending on the image type, interpretation method, time of year, and sampling method applied. Seasonal variation was significant. S190A products obtained in September yielded higher gains than those obtained in June. Using 100 primary sample units as a base under simple random sampling, the revenue made available for incorporating space acquired data into the sample design to estimate timber volume was as high as $39,400.00
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Extraction of anthropological data with ultrasound
This thesis was submitted for the degree of Doctor of Philosophy and was awarded by Brunel University.Human body scanners used to extract anthropological data have a significant drawback, the
subject is required to undress or wear tight fitting clothing. This thesis demonstrates an
ultrasonic based alternative to the current optical systems, that can potentially operate on a fully
clothed subject. To validate the concept several experiments were performed to determine the
acoustic properties of multiple garments. The results indicated that such an approach was
possible.
Beamforming is introduced as a method by which the ultrasonic scanning area can be increased,
the concept is thoroughly studied and a clear theoretical analysis is performed. Additionally,
Matlab has been used to demonstrate graphically, the results of such analysis, providing an
invaluable tool during the simulation, experimental and results stages of the thesis.
To evaluate beamfoming as a composite part of ultrasonic body imaging, a hardware solution
was necessary. During the concept phase, both FPGA and digital signal processors were
evaluated to determine their suitability for the role. An FPGA approach was finally chosen,
which allows highly parallel operation, essential to the high acquisition speeds required by some
beamforming methodologies. In addition, analogue circuitry was also designed to provide an
interface with the ultrasonic transducers, which, included variable gain amplifiers, charge
amplifiers and signal conditioning. Finally, a digital acquisition card was used to transfer data
between the FPGA and a desktop computer, on which, the sampled data was processed and
displayed in a coherent graphical manner.
The beamforming results clearly demonstrate that imaging multiple layers in air, with
ultrasound, is a viable technique for anthroplogical data collection. Furthermore, a wavelet
based method of improving the axial resolution is also proposed and demonstrated
Digital images forever: implementing an imaging system in a cultural institution
This paper deals with the decision-making and challenges that arose out of the implementation of a large-scale digital imaging project by the Powerhouse Museum. With the implementation of the Powerhouse's Imaging Project came the creation of its Image Centre. This paper discusses its role, the services provided, preparation of its equipment and the procedures developed for capturing, storing and retrieving images. Most importantly, the issues of technological change upon an image archive are discussed. The Powerhouse Museum's Imaging System, as it stands today, does what was intended. It delivers images and related data to staff and public for the purposes of research, promotion, education and more. The Museum's Image Centre was set up to scan, manipulate, print and archive images. This Centre has evolved into a high-resolution digital imaging service and continues to create and upload images to the Imaging System. However, without a plan for constant review and update, even archives of beautifully scanned images and comprehensive data are worthless if those archives cannot be reused because the mechanisms for accessing the media - or the applications that they run on, have become obsolete. The Museum's next step, therefore, is a policy for regular re-evaluation.Hosted by the Scholarly Text and Imaging Service (SETIS), the University of Sydney Library, and the Research Institute for Humanities and Social Sciences (RIHSS), the University of Sydney
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