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A method for classifying stellar spectral types based on the statistical moments of objective prism images is described. The results of testing the method on microdensitometer scans of objective prism spectra is given and their significance discussed. Some of the image moments offer a possible way of assigning quantitative spectral classes to large numbers of stars in a short period of time.

Reinstallation of the Sheffield Gamma Knife Unit was completed in early November, 1991, following the replacement of the cobalt sources. Two methods were used to evaluate the isodose configuration within the replenished unit. The first method used a scanning microdensitometer to interrogate films exposed within a spherical phantom, whilst the second relied upon a series of measurements obtained with an array of diodes. The results produced by the latter method compared more favorably with the computer-generated theoretical curves. The two sets of results are presented and some possible explanations for the discrepancies are proposed.

The distribution of zero crossings for the profile of a statistically rough surface of a silver thin film is determined and compared with a Poisson distribution. It is shown that the density of zero crossings may be related to the autocorrelation length and might be a useful parameter for characterizing spatial information of statistically rough surfaces.

Photographic film was used to measure low intensities of guided light scattered from three different thin-film optical waveguides. The technique is shown to permit measurement of optical loss down to 0.07 dB/cm. The method involves the taking of a photograph of a guided light beam (lambda = 632.8 nm) and the use of a microdensitometer to measure the two-dimensional scattered intensity profile. The sensitivity of the photographic film permits the measurement of low light levels, and the beam profile information permits the evaluation of the uniform scattering assumption. The technique can be adapted to channel waveguide loss by using high-definition photographic film. Additionally, the use of infrared-sensitive film can permit the technique to measure loss in the infrared.

It has been proposed to use the 220 reflection of LiF with a multilayer deposited upon the top for simultaneous spectroscopy near Fe-k and O-k and below the C-k absorption edge (284 eV) in x-ray astronomy. We demonstrate that a substantial reduction of surface roughness is obtained by dip lacquering state-of-the-art polished LiF(220) surfaces. Using a microdensitometer analysis of electron micrographs of surface replicas and x-ray reflection, we have measured approximately 10-A rms roughness of Au-coated dip-lacquered LiF(220) crystals, as opposed to approximately 60 A measured on the bare LiF(220) crystal surface.

We have analyzed the principal sources of noise in a commercially available 2-D scanning microdensitometer which we use to estimate the noise power spectra of radiographic films. Two kinds of noise have been observed. One source, associated with the glass platen of the instrument, is correlated from scan to scan. This source of noise limits our ability to measure the NPS of film samples at low sample optical densities. The other major noise source is uncorrelated from scan to scan and increases exponentially with sample optical density. We have measured both of these component noise sources as well as the total instrument noise as a function of instrument density and spatial frequency. A method for minimizing the effects of instrument noise on estimates of the noise power of film samples is described and demonstrated.

This paper deals with the accurate determination of height and slope distributions for surfaces of rough metallic deposits (magnesium, copper, silver, and gold). These distributions are computed using a microdensitometer analysis of electron micrographs of surface replicas. It is shown that most of the surfaces examined have reasonable Gaussian height and slope distributions. Apart from magnesium surfaces, the rms roughnesses determined from these distributions agree (within the accuracy range of their measurements) with rms roughnesses deduced from the autocovariance functions computed previously. Within the framework of scalar scattering theory, some emphasis is laid on the value of slopes to draw certain conclusions about the validity of the assumptions under which the scalar scattering theory is derived.

When the noise power spectrum (NPS) of a radiographic screen-film system is measured by microdensito-metrically scanning the film with a long narrow slit, sufficient slit length allows estimation of a section of the 2-D NPS from the 1-D film scans; insufficient length causes underestimation of the NPS, particularly at low frequencies ( greater, similar1 cycle/mm). Spectra of Hi-Plus, Par Speed, and Detail screens used with XRP films measured as a function of microdensitometer slit length tended to plateau at long slit lengths. The slit length was considered sufficient when NPS components at 0.4 cycle/mm were within 5% of the plateau. This occurred for slit lengths of at least 4.2, 2.6, and 2.5 mm for Hi-Plus, Par Speed, and Detail systems, respectively.

Phase-locked moire systems have the advantage of rapid data acquisition and accuracy of better than one twentieth of the fringe spacing. In conventional moire systems data acquisition is performed by making a photographic plate and taking measurements from the plate either visually or with a microdensitometer. This is slow, and the accuracy is about one-quarter of the fringe spacing. The phase-locked system is more accurate and permits a more favorable trade-off between accuracy and working depth. The equations governing moire contouring are examined, and the theory of phase-locked moire fringe analysis is presented. The design and operation of the phase-locked moire contouring system are described, and the results of measurements made with the instrument are presented.

Coherent optical systems are of interest in image or data processing because of their ability to handle rapidly large bandwidth data in parallel. They have been restricted to performing linear operations such as Fourier transformation and convolution due to the inherent linear nature of an optical system at low power levels. In this paper, the combination of a nonlinear halftoning step followed by bandpass spatial filtering to yield a specific nonlinear intensity transfer function is explored. A general analysis of the problem assuming infinite copy film gamma and saturation density is made. A constructive algorithm for designing a halftone cell shape and selecting the diffraction order to yield very general types of nonmonotonic nonlinearities is presented. Numerous examples of the synthesis procedure are given. Experimental results with general halftone screens made on a plotting flatbed microdensitometer are presented. Logarithmic, exponential, and level slice characteristics are achieved with monotonic cells.

A modulation transfer function (MTF) measuring technique is described that employs the optical matched filter (OMF). It is shown that this technique is mathematically equivalent to the multiple-sine-slit microdensitometer (MSSM) MTF measurement approach. Similarities and differences in the implementation of the two methods are discussed. Both theoretical and experimental matched filter results are investigated. A method for extending the OMF to high spatial frequencies is discussed.

Compensation of mode velocities in optical waveguides can be achieved by fabricating fibers having graded refractive index cores. One technique for measuring these index profiles is interference microscopy. We have developed a machine aided method for analysis of interference micrographs for the rapid determination of optical waveguide refractive index profiles. Our method consists of digitizing the interference micrograph with a scanning microdensitometer, followed by computer determination of the position of the center line of each fringe. The data obtained are then converted into refractive index and fiber radius information, which is used to calculate a best fit power law function.

By means of the Multiple-Sine-Slit Microdensitometer (MSSM), MTF's up to 1500 c/mm have been evaluated for five photographic plates for holography, Agfa-Gevaert Scientia 10E75, 8E75, 8E75B, and Kodak 649-F and Type 120-02. For comparison, an as-if-MTF has also been derived from diffraction efficiency measurements. In addition sensitivity at lambda = 633 nm, the macroscopic characteristic tau(A) vs logE and alpha(2)(E), and scattered-flux data are reported for these five plates.

Microdensitometer measurements of photographic film transmittance made at high spatial frequencies demonstrate that the basic instrument is nonlinear in that its response is a function of the spatial frequency and the mode of illumination. A method developed for measuring the spatial coherence, making use of a Wollaston prism shearing interferometer, has been applied to typical microdensitometers, documenting the existence of the partial coherence. The trace of a phase edge was found to be a graphical means of demonstrating one of the consequences of the partial coherence. Since partial coherence is present in all image-forming instruments, a linear instrument that avoids the imaging step and collects all the transmitted light has been developed. This linear instrument is limited in spatial frequency only by the size of the scanning spot. The system transfer function is the Fourier transform of the scanning spot irradiance. A linear microdensitometer was assembled on an optical bench using a cw laser source and standard microscope objectives, and it was used to trace a series of samples to test its response at high spatial frequencies. The linearity is demonstrated with both edge width measurements and flat response to a phase edge.

An automated technique has been developed for the analysis of various types of interferograms. The technique makes use of a high speed digitized microdensitometer to scan the interferograms and a high speed computer to perform the required computations. The optical thickness variations for a test specimen can be determined by analysis of one or two interferograms. In addition, when required, determinations can be made of time change in optical thickness or the physical thickness and index of refraction homogeneity profiles by analysis of multiple interferograms.

The quality of portal imaging is strongly affected by the source size of the radiotherapy machine. The effective source size of the dual‐energy clinac 1800 (6 and 18 MV) was measured with a 50 μm wide and 120 mm long slit formed by two tungsten‐copper alloy blocks. A series of slit images were obtained by translating the slit horizontally. The images were analyzed using a microdensitometer. The measured data was simulated using an analytical model of the source and its size was derived by a best‐fit analysis. For both energies the FWHM was found to be 1.5±0.1 mm.

An impactor/concentrator/microdensitometer (ICM) instrument system has been constructed and calibrated. This system is sufficiently sensitive to measure the black (carbon soot) component of Antarctic aerosol with a sampling time of four hours. The impactor concentrator was exposed to Antarctic air at Ross Island in September 1987. Microdensitometer analysis of the collected specimens indicates that the maximum black aerosol concentration was observed concurrently with the arrival of the warmest air accompanying a cyclonic storm. This is similar to the concurrence of continental radon and lead isotopes with warm advection, measured on the Antarctic coast by Polian et al. (1986). It is possible that continental soot can be transported to the Antarctic coast several times each year by this mechanism.

Summary The experimental methodology and data analysis techniques used to characterize the performance of a sabot/rod as it is subjected to lateral and axial loading during launch is presented. The experimental portion of the research involved full-scale testing of two separate sabot/rod designs in a 120-mm launch tube that was slightly bent. When launched through the bent tube, the sabot/rod system was forced to negotiate lateral displacements at axial velocities of approximately 1650 m/s. This combination of axial velocity and lateral displacement produced significant lateral loading on the sabot/rod system. A 2.3-MeV X-ray unit was used to determine the lateral displacement that occurred as the sabot/rod was forced through the bent tube. After the sabot/rod exited the launch tube, the sabot separation and rod straightness were recorded by four 150-keV X-ray units. The inbore radiography experiments used X-ray shielding techniques to reduce X-ray scatter, and layered indexed film and intensifier screens to record the sabot/rod image. The processed film was computer scanned with a microdensitometer and was remapped on the computer to enhance the X-ray image. Results indicated rod lateral displacement accuracy to 0.11 mm. Test results were used to determine the sabot and rod behavior caused by loading histories of axial and lateral impulsive loadings.

Autocorrelation functions for rough surfaces of evaporated opaque magnesium deposits are determined from electron microphotographs of the shadowed-surface carbon replicas. These microphotographs are analyzed, using a data-processing system microdensitometer. It is shown that autocorrelation functions do not have a Gaussian form, as is usually assumed.

Screen-film systems are used in mammography even now. Therefore, it is important to measure their physical properties such as modulation transfer function (MTF) or noise power spectrum (NPS). The MTF and NPS of screen-film systems are mostly measured by using a microdensitometer. However, since microdensitometers are not commonly used in general hospitals, it is difficult to carry out these measurements regularly. In the past, Ichikawa et al. have measured and evaluated the physical properties of medical liquid crystal displays by using a high-performance digital camera. By this method, the physical properties of screen-film systems can be measured easily without using a microdensitometer. Therefore, we have proposed a simple method for measuring the MTF and NPS of screen-film systems by using a high-performance digital camera. The proposed method is based on the edge method (for evaluating MTF) and the one-dimensional fast Fourier transform (FFT) method (for evaluating NPS), respectively. As a result, the MTF and NPS evaluated by using the high-performance digital camera approximately corresponded with those evaluated by using a microdensitometer. It is possible to substitute the calculation of MTF and NPS by using a high-performance digital camera for that by using a microdensitometer. Further, this method also simplifies the evaluation of the physical properties of screen-film systems.

We have examined a sample consisting of 41 ultraluminous IRAS galaxies with far-infrared luminosities LIR > 10(12) L. (H0 = 50 km s-1 Mpc-1), and a control sample of 41 low-luminosity IRAS galaxies with LIR 0.6 Jy. Their images on the film copies of the SERC Sky Survey were scanned with a pixel size of 5-mu-m (0.34 arcsec) over a square area of typically 67.2 arcsec to the side, using the microdensitometer PDS of the Purple Mountain Observatory. The density contour maps and the sky survey material show that the proportion of ultraluminous IRAS galaxies which are interacting or merger systems, 61 +/- 12 per cent, is much higher than that of low-luminosity ones (10 +/- 5 per cent), but still well short of the 100 per cent suggested in several recent reports. This result seems to support the conclusion that galaxy interaction or merging is more common at high-IR luminosity, but it is probably not the only cause of their activity.

An extended granularity model for single layer colour coatings is presented, which allows all quantities characterizing granularity to be calculated from coupler and coating parameters. It represents a combination of the kinetical theory of dye cloud formation with existing granularity theories. In the first step, the dye concentration within an isolated dye cloud is calculated by solving a reaction/diffusion equation for quinonediimine. It is shown that at least three measurable quantities can be derived from the dye distribution: the two-dimensional density profile of a dye cloud and the relative noise power spectrum, by appropriate integration over this distribution, and the absolute granularity-density curve, by Monte-Carlo-simulation. These three quantities were measured for a set of model layers, two of them being discussed in this paper, by a high-resolution microdensitometer allowing sub-micron scanning. Satisfactory agreement with the calculated curves was found for each of the three quan...

In order to produce radiographs with controlled image quality, among other factors, it is important to know and to be able to monitor any changes in the actual size of the radiation source. This article describes a simple and practical method for the determination of source sizes which can be conveniently applied in any radiographic testing shop or even in the field. The use of a microdensitometer often needed for focal spot size measurements is avoided. In addition to three different X-ray tubes an iridium 192 source is used in this study. Focal spot size measurements were conducted at various energy levels and experimental conditions. It is observed that the measured values of focal spot sizes were larger than their nominal values, and were also affected by the level of the tube voltage.

We have carried out an astrometric test of the 1.56m reflector of Shanghai Observatory. Two plates of the Pleiades region were taken and the images were measured with a PDS microdensitometer. Referring to the positions given in Eichhorn's catalogue as, standards and using a cubic reduction formula, we find the positions within ±14' of the centre are determined with an accurcy of 0.03″, and within ±16', an accuracy of 0.04″. A comparison with the Mexican 2.12m reflector is made. In addition, the coefficient of the coma term in the plate constants is found to be on the order of 10−4–10−5 and that of the distortion term, on the order of 10−8–10−9. These figures indicate that the 1.56 R-C Reflector is well fitted to undertake astrometry of faint objects.

A calibration of three types of GafChromic radiochromic film (HS, MD-55, and HD-810) was carried out on the Crocker Nuclear Laboratory's 76 in. cyclotron at UC Davis over doses ranging from 0.001 to 15 kGy. The film was digitized with a scanning microdensitometer with which it was scanned twice with two different filters to increase the film's effective dynamic range. We demonstrate how this calibrated film can be used to measure the spectrum and total energy of a laser generated proton beam. This technique was applied to an experiment on the 10 J, 100 fs Callisto laser at Lawrence Livermore National Laboratory. The resulting proton spectrum was compared to that obtained by simultaneous measurement of Ti nuclear activation; the two methods give the same proton beam slope temperature and agree in number of protons to within 27%.

A flatbed reflection scanner is a tempting device to use as a surrogate for a microdensitometer in the evaluation of print image quality. Since reflection scanners were never designed with this purpose in mind, many concerns exist regarding their usefulness as a microdensitometer surrogate. This paper addresses the concerns regarding scan uniformity that must be addressed in order to qualify a reflection scanner for use in print image quality evaluation.

In this paper the importance of measuring dimension from neutron radiographs of nuclear reactor fuel is explained. Measurements are taken using either a profile projector or a traveling microdensitometer. Neutron radiographs are made by the direct, transfer, and track-etch techniques, the last two being used for radioactive objects such as spent reactor fuel. The accuracy of these measurements was investigated during the Euratom Neutron Radiography Working Group Test Program. Measuring results are discussed for different kinds of nuclear fuel pin dimensions and 30 different combinations of recording materials. The accuracy of the measurements is assessed by calculating standard deviations between the dimensions determined from neutron radiographs and the true dimensions of a calibration fuel pin.

The photographic emulsion is one of the oldest detectors used in atomic emission spectroscopy. Although overshadowed by modern electronic detectors for quantitative measurements, there remain significant advantages in their use for qualitative spectroscopic studies. Relative to direct reader and electronic image detector (i.e., photodiode array and charge-coupled device) simultaneous multichannel measurement schemes, photographic emulsions provide considerably greater detection flexibility for qualitative analytical determinations. Their large physical size and low cost allow simultaneous measurements with resolution and wavelength coverages that are not attainable with any other system (and at a cost that any research program can afford). Admittedly, the nonlinear response of the photographic emulsion to emission intensity requires the use of complex calibration schemes for quantitation, but for qualitative spectroscopic information, no other detector scheme can acquire the amount of information that this simple two-dimensional detector can.

Previous video-light microscopic studies have shown that the microtubule bundles in the pseudopodia of foraminiferan protists display several types of movements in vivo , including active bending, zipping/splaying, and axial translocations. To gain insight into the types and arrangement of microtubule-associated proteins ( e.g. , mechanoenzymes, crosslinkers) in such a highly dynamic system, we employed microdensitometric-computer correlation methods to analyze, quantitatively, intermicrotubule bridges in thin-section electron micrographs of Allogromia laticollaris and Allogromia sp. (strain NF). Two distinct bridges occupying mutually exclusive zones between adjacent microtubules were identified. Type I bridges displayed a single axial repeat (34 nm for A. laticollaris and 28 nm for Allogromia sp.) and Type II bridges showed a typical 12-dimer helical superlattice pattern. In A. laticollaris , the two types of bridges were morphologically distinct: Type I bridges were aligned perpendicular to the microtubule wall and were 23-nm wide with an electron-lucent core; Type II bridges were irregular filaments projecting from the microtubules at various angles. When compared with the known distribution of microtubule-associated proteins in other systems, our findings indicate that, in viuo, Allogromia pseudopodial microtubules are decorated with MAP2-like bridges interrupted by discrete clusters of a dynein-like component.

It was previously shown how the fractal nature of thin‐film top surfaces can be obtained from the surface relief reconstructed by microdensitometer analysis of an electron micrograph of a shadowed replica of the surface. Here, we present some improvement in the determination of the fractal dimension Dl which characterizes a planar section of the thin film, as well as a different way of conducting such a determination. Results connected with several rough thin films are given and it is found that many different ways of characterizing the fractal nature of a thin‐film top surface are possible from the reconstructed relief of the surface to be studied.

Photographic spectra of SN1987A in the LMC have been obtained from 1987 February 25 to 1988 June 30. Microdensitometer tracings of these have been reduced to intensity and corrections for instrumental response have been applied to the spectra. This paper presents these data in an atlas format, discusses the reduction procedures in detail, and presents radial velocity measurements of selected lines in the spectra

An objective method for reliably estimating the width of retinal vessels is presented. A computerized microdensitometer scans film negatives of fundus photographs and reconstructs black and white images of the fundus on a visual display terminal. After this initial scan, a desired region of a retinal vessel is selected with moveable cursors, and a cross-sectional density profile through the vessel is plotted. Vessel width is determined by the half-height width of the profile of the minimum (least transmitting) and average background film densities. Measurement sites can be accurately reproduced on different negatives by landmark mapping. A series of ten fundus photographs were taken of three healthy human eyes, and the width of the superior temporal vein was measured in two places on alle negatives. The coefficient of variation of the six sets ranged from 1.2 and 3.4% with an average of 2.2%.

The purpose of this study was to determine the effect of initial periodontal therapy on crestal bone remineralization with the use of a digital subtraction method for quantitative analysis. Fifteen crestal sites randomly selected from five patients were examined at the initial visit, after completion of oral hygiene instruction, and 1, 3, and 6 months after scaling and root planing with standardized radiographs. The radiographs were digitized by means of a drum-scanning microdensitometer with a sampling aperture of 50 microns producing 256 gray levels and corrected for difference of contrast between image pairs. Results were as follows: (1) statistically significant changes were observed even 1 month after the therapy and (2) the extent of changes was quantitatively expressed and monotonically increased with time. These results indicate that subtraction radiography may be a reproducible and quantitative method for the evaluation of periodontal therapy.

We present an original method of digitizing and astrometrically reducing "Carte du Ciel" plate material using an inexpensive flatbed scanner, to demonstrate that for this material there is an alternative to more specialized measuring machines that are very few in number and thus not readily available. The sample of plates chosen to develop this method are original "Carte du Ciel" plates of the San Fernando zone, photographic material with a mean epoch 1903.6, and a limiting photographic magnitude ~14.5, covering the declination range of -10 < dec < -2. Digitization has been made using a commercial flatbed scanner, demonstrating the internal precision that can be attained with such a device. A variety of post-scan corrections are shown to be necessary. In particular, the large distortion introduced by the non-uniform action of the scanner is modelled using multiple scans of each plate. We also tackle the specific problems associated with the triple-exposure images on some plates and the grid lines present on all. The final measures are reduced to celestial coordinates using the Tycho-2 Catalogue. The internal precision obtained over a single plate, 3microns ~ 0.18" in each axis, is comparable to what is realized with similar plate material using slower, less affordable, and less widely available conventional measuring machines, such as a PDS microdensitometer. The accuracy attained over large multi-plate areas, employing an overlapping plate technique, is estimated at 0.2"., 16 pages, 19 figures and 3 tables. Accepted for publication in A&A

Radiochromic film has been applied to mapping of dose distributions in radiation therapy. However, this particular RCF product suffers from intrinsic nonuniform response. In this study, we have carefully measured the nonuniformity of unirradiated RCF, and the response of irradiated RCF in pixel-to-pixel as function of various absorbed doses, in order to create a method of predicting the error of irradiated, unirradiated RCF.

Ferrous-sulphate infused gels, or 'Fricke gels', encounter great interest in the field of radiation dosimetry, due to their potential for 3D radiation dose mapping. Typically, magnetic resonance (MR) relaxation rates are determined in these systems in order to derive the absorbed dose. However, when large concentration gradients are present, diffusion effects before and during the MR imaging may not be negligible. In these cases, optical techniques may represent a viable alternative. This paper describes research aimed at measuring 3D dose distributions in a Fricke-xylenol orange gel by measuring optical density with a CCD camera. This method is inexpensive and fast. A series of early experiments is described, in which optical density profiles were measured with a commercial microdensitometer for film dosimetry. The light box of the device was modified to work at 567 nm, close to the maximum absorbance of the ferric ion-xylenol orange complex. Under these conditions, the gel shows linearity with dose and high sensitivity.

Radiochromic film (RCF) has been applied to mapping of dose distributions in radiation therapy. However, this particular RCF product suffers from intrinsic nonuniform response. In this study, we have carefully measured the nonuniformity of unirradiated RCF, and the response of irradiated RCF in pixel-to-pixel as function of various absorbed doses, in order to ascertains for the method of predicting the error of irradiated, unirradiated RCF.

The tissue equivalent composition of the Gafchromic films makes them particularly suitable for the mapping of 2D and 3D treatment fields. This paper presents the results obtained using MD-55 film for the verification of real radiotherapy treatments through proton beam irradiation of suitable phantoms at the Clatterbridge Centre for Oncology (CCO) in Bebington (UK). After exposure, the variation in optical density of the films was measured using a CCD100 Microdensitometer (source at 665 nm). Holes of calibrated diameter, made during the assembly phase of the phantom, are identified by the MIRA software, used for data analysis, and allow the rendering of the films. The surface dose distributions were obtained from the variation in optical density of each of the films making up the phantom. Their elaboration to duplicate their position within the phantom, performed by 3D-doctor software, allows the volumetric reconstruction of the dose distribution.

It is generally assumed that the mass balance between corona and prominences will be exist, but unambiguously observational proofs for a such exchange of material are rare. Especially, there is a little data that can be used to adress the problem of flow mass from prominence to the corona. We relate prominence-corona interface as was obtained in short-term variation of special observations in H-alpha with Lomnick~ stir coronograph. The two different prominence types (quiescent, and highly structured, stable, but not quiescent, like as a surge) were performed with a 20-cm lens coronograph over 24, respectively 17 minutes on 1988 August 28 and 18 (FWHM = 0.8 nm, a 1 minute record). A detailed photometry was made with Joyee-Labell microdensitometer at Ro~en Observatory (a slit 40 x 40 ~m, a step 20 ~m). There were no changes in the outer shape in the quiescent prominence on 1988 August 28 over 24 minutes (isolines, calibrated to the Sun's disk were used). A remarkable, but exceedingly faint changes should be seen in the outer shape on August 18, 1988 prominence. The prominence mass at the top of two curved columns continuously disappeared during lO minutes. One may suppose that this cool prominence plasma was continuously heated to the coronal temperature via some mechanism of heating (fast-mode waves, current dissipation etc.). The total disappeared prominence mass was estimated of 8 x lollg. It is necessary to stress that prominencecorona interface outside of disappeared area, including the first one, did not change over these sequences. It seems that surge-like type of prominence could be a next candidate for a transport of mass from dense underlying layers to the corona (isolated knots od disparition brusque or slowly ascending material connected with flares are the first ones). Prominence areas change over cycle in the same course as the total brightness of the white-light corona (both display their mass) i.e. they are of two times higher (minimally) in the maximum as in the minimum of cycle.

A high-end drum film digitiser (Tango, Germany) and a calibrated linear microdensitometer developed by PTB were used to assess the modulation transfer function (MTF) and the noise power spectra (NPS) of 3 mammographic screen film systems at optical density levels of 0.8, 1.5 and 2.5. The use of a drum scanner to assess MTF and NPS data appears to be adequate but requires an appropriate characterisation of the scanner to verify its internal noise level and its MTF. It is further necessary to calibrate the scanner output in terms of visual diffuse optical densities. Processing of two-dimensional digital data of grating images need to be more strictly defined for accurate MTF measurements of screen-film systems. Nevertheless, even now it seems to be feasible to use commercially available high-end and well calibrated scanners to assess screen film systems. This is especially important for quality assurance purposes because important parameters of screen film systems such like MTF and NPS can now be determined without using sophisticated microdensitometers which are not commercially available.

Inexpensive and easy-to-use linear and area-array scanners have frequently substituted as densitometers for low-frequency (i.e., large-area) hard copy image metrology. Increasingly, they are also being tasked for high spatial frequency, image microstructure metrology, which is reserved for high-performance microdensitometers that use microscope optics, photomultiplier tubes (PMT), and log amps. It is hard to resist their adoption for such use though, given the convenience level. Their high speed, large scan areas, auto-focus, discomfiting low cost, and low operator skill requirements makes one question if their use for such purpose is somehow too good to be true. To confidently judge their limitations requires a comprehensive signal and noise spatial frequency performance evaluation with respect to available driver options. This paper will outline and demonstrate evaluation techniques that use existing ISO metrology standards for modulation transfer function (MTF), noise, and dynamic range with a comparison to a Photometric Data Systems (PDS) microdensitometer

Radiation dose deposited on a radiochromic film is considered as a dose image. A precise image extraction system with commensurate capabilities is required to measure the transmittance of the image and translate it to radiation dose. This paper describes the development of a spectral microdensitometer which has been designed to achieve this goal under the conditions of (a) the linearity and sensitivity of the dose response curve of the radiochromic film being highly dependent on the wavelength of the analysing light, and (b) the inherent high spatial resolution of the film. The microdensitometer consists of a monochromator which provides an analysing light of variable wavelength, a film tray on a high-precision scanning stage, a transmission microscope coupled to a thermoelectrically cooled CCD camera, a microcomputer and corresponding interfaces. The measurement of the transmittance of the radiochromic film is made at the two absorption peaks with maximum sensitivities. The high spatial resolution of the instrument, of the order of micrometres, is achieved through the use of the microscope combined with a measure-and-step technique to cover the whole film. The performance of the instrument in regard to the positional accuracy, system reproducibility and dual-peak film calibration was evaluated. The results show that the instrument fulfils the design objective of providing a precise image extraction system for radiochromic films with micrometre spatial resolution and sensitive dose response.

A film-handling machine (robot) has been built which can, in conjunction with a commercially available film densitometer, exchange and digitize over 300 electron micrographs per day. Implementation of robotic film handling effectively eliminates the delay and tedium associated with digitizing images when data are initially recorded on photographic film. The modulation transfer function (MTF) of the commercially available densitometer is significantly worse than that of a high-end, scientific microdensitometer. Nevertheless, its signal-to-noise ratio (S/N) is quite excellent, allowing substantial restoration of the output to ''near-to-perfect'' performance. Due to the large area of the standard electron microscope film that can be digitized by the commercial densitometer (up to 10,000 x 13,680 pixels with an appropriately coded holder), automated film digitization offers a fast and inexpensive alternative to high-end CCD cameras as a means of acquiring large amounts of image data in electron microscopy.

Summary form only given, as follows. The polar distribution of X-rays emitted by a Z-pinch has been inferred from the darkening of radio chromic film exposed on Double Eagle. For these measurements, a 3 cm wide film was mounted on a 72 cm radius arc with one end at the mid plane of the 2 cm long Al wire pinch. The width of the film was covered by three strips, 1 cm wide, of aluminized Kapton foil having one, two and three layers 8.3 /spl mu/m each over the entire 35 cm length of arc. These three layers of Kapton filtered out the UV radiation and provided three levels of film exposure at each angular position. The exposed radio chromic film was scanned with a microdensitometer and the results displayed as three curves of optical density (OD) variation with angle from the mid plane. The calibration procedure assumed that the same optical density results on different regions of radiochromic film filtered by different Kapton filters if the energy density on the film is the same in each case, ie: if U(/spl theta//sub n/)T/sub /spl alpha//=U(/spl theta//sub m/)T/sub /spl beta//. This allows us to relate the energy density U(/spl theta//sub n/), at a finite number of angular position /spl theta//sub n/ to the energy density at the mid plane as a combination of transmission ratios through the three Kapton filters. By adjusting the values of the transmission ratios, a smooth emitted intensity profile is obtained. The intensity is observed to decrease significantly more rapidly with angles from the mid plane than the cosine dependence that is expected. This variation may be indicative of radiation characteristics not currently considered. It also implies that the fluence near the mid plane may be higher than the value inferred from measurements made at some angle below it.

This work presents a computational model for practical application of the transfer function method for radiographic units evaluation, in order to reduce some experimental constraints involved to its determination. With the proposed algorithm, the complete Optical Transfer Function (Modulation Transfer Function and Phase Transfer Function) can be easily determined as well as the effective focal spot sizes at any field location without using a microdensitometer. All measurements are done from a digitized slit image obtained experimentally at the field center position. The effective focal spot sizes can be calculated by using the Line Spread Function Root Mean Square (RMS) value or by the Modulation Transfer Function (MTF) first minimum. Besides, considering the variation of the effective focal spot size given by the field characteristic equations, all these parameters can also be determined at any location on the radiation field. The computer scheme was used for evaluating slit images obtained from nine different x-ray equipments. Results confirmed the possibility of using the transfer function method for quality evaluation of any radiological system in a simple and automatic way. This computer scheme replaces some of the expensive and specific devices necessary to the experimental MTF evaluation by quite more accessible and low cost equipments.