Unsharp Masking Technique Research Articles

The extended red emission filaments in NGC 2023

Using the photographic unsharp masking technique and image cancellation, the high-frequency surface brightness fluctuations in the reflection nebula NGC 2023 have been imaged over 406 arcsec x 510 arcsec field. Maps with 1 arcsec resolution, centered on the illuminating star HD 37903, are presented for the photometric B and R bands. A system of narrow filamentary structures observable only in the R band are identified as extended red emission (ERE) features. These features are not associated with any apparent density enhancements in the nebula. Arguments are presented which link the ERE filaments to regions within the nebula where photodissociation of molecular hydrogen occurs.

NGC 362 - More arguments for dust in globular clusters

view Abstract Citations (8) References (12) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS NGC 362: More Arguments for Dust in Globular Clusters Mendez, Mariano ; Forte, Juan C. ; Orsatti, Ana M. Abstract Following the detection of dust clouds in several globular clusters (Forte and Mendez), we present new U CCD data of the southern globular cluster NGC 362. Image processing shows the existence of dark patches distributed asymmetrically around the center of the cluster. Three different types of arguments are used to identify these patches as dark clouds within the cluster, namely (1) color mapping; (2) improved resolution images using modified unsharp masking technique; (3) behavior of the apparent extinction with wavelength. Finally, a total dust mass of about 0.1 solar mass is estimated for the cloud complex. Publication: The Astrophysical Journal Pub Date: March 1989 DOI: 10.1086/167186 Bibcode: 1989ApJ...338..136M Keywords: Astronomical Photometry; Cosmic Dust; Globular Clusters; Ultraviolet Astronomy; Charge Coupled Devices; Interstellar Gas; Southern Sky; Astrophysics; CLUSTERS: GLOBULAR; INTERSTELLAR: GRAINS full text sources ADS | data products SIMBAD (1)

Digital image processing of dentomaxillofacial radiographs

The improvement in the image quality of dentomaxillofacial radiographs (panoramic radiographs) with the use of a digital image-processing system was examined. Linear and nonlinear unsharp masking techniques were employed for image processing. The quality of the processed images was found to be markedly improved over that in original radiographs. The detail visibility of linearly enhanced images, especially in low-density areas, was superior to that of nonlinearly enhanced images, although the presence of more artifacts and more noise was noted in linearly enhanced images. Radiographic diagnosis in the dentomaxillofacial region can be improved with this system.

Digital beam attenuator technique for compensated chest radiography.

The feasibility of producing patient-specific beam attenuators for chest radiography has been investigated using an anthropomorphic phantom and a human volunteer. A low-dose test exposure is digitized, processed, and used to print a small cerium filter, which is placed in the x-ray beam near the collimator. The final radiograph is recorded on film. The technique results in relatively uniform film exposure, so that structures in all regions of the chest are simultaneously displayed with optimal film contrast. The equalized exposure improves image quality in the normally underpenetrated regions and reduces the role of cross-scatter from the lungs. The image is analogous to optical or computer-processed unsharp masking techniques, but the processing is accomplished in the x-ray beam and results in an improved exposure distribution, giving advantages that cannot be achieved with image processing techniques alone.

Investigation of basic imaging properties in digital radiography. 4. Effect of unsharp masking on the detectability of simple patterns.

The signal-to-noise ratios (SNRs) of simple radiologic patterns processed by the unsharp-masking technique were calculated on the basis of a statistical decision theory model that includes both the observer's visual transfer function and a noise component internal to his eye-brain system. For a variety of processing parameters, the contrast-detail diagrams predicted from this SNR agreed qualitatively with experimental results obtained in observer performance studies. Unsharp masking with a large mask and a large weighting factor improved the detection of square objects to a level comparable with that achieved by the overall contrast enhancement technique using a factor of 4. However, unsharp masking with a small mask and a large weighting factor can substantially degrade the detectability of these objects. The potential practical utility of the unsharp-masking technique is discussed.

Photographic Unsharp Masking in Chest Radiography

A photographic unsharp masking technique for improving the latitude of chest radiographs without sacrificing image contrast or detail is described. An unsharp mask film, prepared from a scout film of the patient's chest, is placed between the film and the front (entrance) screen in the cassette. A second radiograph then is recorded using technique factors that provide a well-penetrated view of the central mediastinum, etc. The unsharp mask absorbs light from the screen in those areas of the chest that normally are well penetrated, preventing overexposure of these areas and resulting in an improved balance of densities across the chest image. Improvement of contrast by a factor of 2 is demonstrated for mediastinal and retrocardiac structures with no loss of contrast in the central lung fields. Nodule detection studies with a chest phantom and simulated nodules suggest that a single unsharp masked film provides higher nodule detection rates than a pair of films consisting of a normally penetrated and an overpenetrated view, possibly because of facilitation of visual search patterns and contrast/brightness adaptation mechanisms of the visual system. Initial clinical studies indicate that unsharp masking may provide additional useful clinical information.

Unsharp masking and related image enhancement techniques

Unsharp masking-in many forms-is a frequent technique in image enhancement. Various versions of unsharp masking are described together with the related dynamic exposure control techniques. Detailed analyses of these techniques are appended.