Image quality

Image or print quality in any form of textile piinting will consider the appearance and color of the print as well as print permanence, usability, or cost. Print issues may relate to the original design file, the conversion software for the printer, inconsistent fabric feed through the printer, fabric pretreatments, and fixing or finishing rather than ink formulations. Visual analysis of ink performance as a print combines specific 

Color must be assessed for any shift in hue from the original design file. Hues can be grouped to consider which colors or families may be problematic. Any color shift toward a particular family, e.g., a shift to blue, may be caused by a fabric pretreatment with optical whitener or may indicate limitations in the color profiling. As well as clarity, resolution involves the rendering of detail using contrast between different 

There are quite a few metrics that lithographers use to quantify the quality of an image. These include the contrast, modulation transfer function, exposure latitude. 

One solution to the problem is to increase the ionization probability. This can be done by choosing primary ions with heavy mass, for example, Bi+ or even C so+, which contains 60 carbon atoms. The noise level can also be reduced by techniques of digital image processing. For example, a fast Fourier transform technique has been used to remove noise from the image. This technique transforms an image from a space domain to a reciprocal domain by sine and cosine functions. Noise can be readily filtered out in such domain. After a reverse Fourier transform, filtered data produces an image with much less noise. 

---

The detectability of critical defects with CT depends on the final image quality and the skill of the operator, see figure 2. The basic concepts of image quality are resolution, contrast, and noise. Image quality are generally described by the signal-to-noise ratio SNR), the modulation transfer function (MTF) and the noise power spectrum (NFS). SNR is the quotient of a signal and its variance, MTF describes the contrast as a function of spatial frequency and NFS in turn describes the noise power at various spatial frequencies [1, 3]. 

Cohen, G. and F.A. DiBianca, The use of contrast-detail-dose evaluation of image quality in a computed tomographic scanner. Journal of Computer Assisted Tomography, 1979. 3(2) p. 189-195. 

Sekihara, K., H. Kohno, and S. Yamamoto, Theoretical prediction of x-ray CT image quality using contrast-detail diagrams. IEEE Transactions on Nuclear Science, 1982. NS-29(6) p. 2115-2121. 

A New US Film System Classification and Image Quality Assessment. 

Contrast Sensitivity S For this purpose a test piece is used whose least material thickness to be resolved in the video signal corresponds to the contrast sensitivity. The test piece can be a step/hole image quality indicator as per EN 462-2. 

In general, the performance of a radioscopic system should always be checked via test pieces with natural flaws. To ensure an additional comparability, standardized image quality indicators have to be used to control the essential image quality parameters such as spatial resolution (unsharpness) and contrast sensitivity. 

The image quality of CR is clearly better than attained by usual radioscopic systems which... 

Luminescence IP s are fundamentally and theoretically utilizable for nondestructive testing if all of the recommended guidelines and operational recipes and appropriate systems are used. They are quite capable of producing image quality on a par with industrial radiography. 

A 3D summation tomographic image is generated and layers in any direction may be viewed. Image quality is improved by filters. The method has been proved satisfactory on a high radiographic contrast cylindrical object and on more complex items. 

Cohen B., Improving Analog CT Image Quality , 1991, Research Thesis, Doctor of Science, The Department of Quality Assurance and Reliability,. Technion. 

To evaluate the image quality of the processing system, one can determine classical parameters like spatial resolution, contrast resolution, dynamic range, local and global distortion. Guidelines for film digitization procedures have been well described now. Furthermore, a physical standard film for both equipment assessment and digitization calibration and control, will be available in a next future (4). 

In case of some samples besides the cross sectional CT-slice also a projectional image is of interest. In these cases the test mode Digital Radiography (DR) is applied. In the DR-mode the object is not turned, but scanned horizontally and vertically. Again the very high dynamic of the detector and the mechanical accuracy of the complete system are of large benefit to the image quality. 

It has been found that the contrast in film density caused by very small local variations in mass density of the concrete is considerable, e g. S D = 0.12 for a 6 mm diameter hole in a 250 mm thick concrete beam. The image quality provided by fine-grained films (Agfa Gaevert D7) was sufficient to distinguish the thin walls of a pre-stressing duct in a 750 mm thick concrete bridge slab. 

The construction of an aberration-corrected TEM proved to be teclmically more demanding the point resolution of a conventional TEM today is of the order of 1-2 A. Therefore, the aim of a corrected TEM must be to increase the resolution beyond the 1 A barrier. This unplies a great number of additional stability problems, which can only be solved by the most modem technologies. The first corrected TEM prototype was presented by Flaider and coworkers [M]- Eigure BE 17.9 shows the unprovement in image quality and interpretability gained from the correction of the spherical aberration in the case of a materials science sample. 

In practice image quality is also reduced by use of high mass resolution and energy offset. Often, therefore, mass interference cannot he avoided. Determination of element distributions is possible by use of image processing tools for classification of mappings of different masses [3.53]. 

A useful measure of imaging quality is the Strehl ratio. It is defined as the ratio of the on-axis intensity in the image of a point source, to that given by the diffraction limited system with the same aperture. A phase aberration (p x) will result in a Strehl ratio of... 

The idea to produce a converging objective from a reflecting, concave surface, instead of a refractive lens, was recognised by Galileo himself, and tried by Zucchi in 1616 (Fig. 4). Such arrangement, however, does not deliver acceptable image quality as a spherical surface used off-axis produces strong aberrations, and Zucchi s attempt was doomed for reasons he could not know. 

---