Reciprocity Law Failure Research Articles

Framework for predicting the photodegradation of adhesion of silicone encapsulants

We developed a framework to predict and model the photodegradation of adhesion and cohesion of a silicone encapsulant for concentrator photovoltaic applications. Silicone encapsulant specimens were artificially weathered under narrow band UV filters to determine the effects of individual wavelengths within the UV spectrum on the photodegradation of the cohesion of encapsulant material and its adhesion with adjacent interfaces. The threshold wavelength, signifying the upper bound of the damaging action spectrum for the silicone, was identified from the results. In addition, specimens were artificially weathered with different relative humidities to understand the effects of moisture on the rate of photodegradation. The adhesion energy was measured using a fracture mechanics approach. The complementary delaminated surfaces were characterized to determine the failure pathway and chemistry changes resulting from photodegradation. A previously developed model was modified to account for the effects of damaging wavelengths in the terrestrial solar spectrum and reciprocity law failure due to varying UV intensity during weathering. With these modifications, the model showed good agreement with the behavior of the silicone encapsulant exposed in an outdoor solar concentrator simulating concentrator photovoltaics operating conditions. Similar studies can be adopted to develop models that can have high predictive accuracies based on accelerated aging studies.

Improvement of ultrafast holographic performance in silver nanoprisms dispersed photopolymer.

This work demonstrates the grating formation of bulk nanoparticle polymer composites through an improved interference optical system under ultrafast nanoseconds exposure of a silver nanoprisms (NPs) dispersed photo-polymerizable mixture in the case of 532 nm wavelength. The polymerizable mixture is composed of phenathrenequinone (PQ) (photoinitiator) and methyl methacrylate (MMA) (monomer). The mechanism in this bulk nanoparticle polymer composite is analyzed by mixing nonlocal polymerization driven diffusion (NPDD) model and absorption modulation caused by the spatial concentration distribution difference of silver NPs. We find that the attenuation of diffraction efficiency under pulsed exposure is due to the reciprocity law failure. This work presents an analysis of the cause of reciprocity failure and improvement in holographic properties by doping silver NPs. The optimized photopolymer presents diffraction efficiencies as high as 51.4% with 1.8 μs cumulative pulsed exposure. Cumulative gratings strength is also enhanced by 70% while doping silver NPs under 1.5 μs cumulative pulsed exposure.

Potential Profile Measurement and Mechanism Analysis of an Electrostatic Latent Image by Detecting Primary Electrons

A new method that makes possible a potential profile measurement of an electrostatic latent image is proposed. When the surface potential is greater than the acceleration voltage of the primary electron, the velocity becomes zero before the electron hits the sample. As a result, the primary electron reaches a detector without reaching the sample. The surface potential profile can be measured by detecting primary electrons while changing the applied voltage to the substrate of a photoconductor. The significant feature of this method is that the charging, exposure, and detection devices are all incorporated in the same system, making real-time measurement possible. In order to confirm the phenomenon of reciprocity law failure, the potential depth of the latent image was measured by changing the delay time when double-pulse exposure was carried out. As a result, the latent image potential tends to be formed deeper as the delay time becomes longer. The developed Electrostatic Latent Image Measuring System (ELIMS) has good performance with a measurement potential resolution of 2 V.

Potential Profile Measurement and Mechanism Analysis of Electrostatic Latent Image by Detecting Primary Electrons

A new method that makes possible a potential-profile measurement of an electrostatic latent image is proposed. The key technology is to detect a primary electron. When a surface potential is greater than acceleration voltage of the primary electron, the velocity becomes zero before the electron hits a sample. As a result, the primary electron reaches to a detector without reaching the sample. The potential distribution can be measured by detecting primary electrons while changing an applied voltage of a backside. This method is that the means of charging, exposing, and detecting are all incorporated in the same system, making real-time measurement possible.This system is being used to analyze the basis of an electrostatic latent image formed on a photoconductor. In order to confirm a phenomenon of reciprocity law failure, the latent-image depth was measured by changing the delay time when exposure was carried out a couple of times. As a result, the latent-image depth tends to be formed deep when the delay time becomes long.

Reciprocity Law Failure of Lithfilm (Part-1)

Reciprocity Law Failure of Lithfilm (Part-1)

SU‐FF‐T‐174: Dose Rate Dependence of Film Dosimetry in Radiation Treatment: Study of Reciprocity Law

Purpose: Film has become an important tool for dose verification in individualized IMRT treatment fields. The optical density (OD) is related to dose rate also known as reciprocity law; (D= Dr*t). However for modern films (EDR and XV) reciprocity law has not been investigated which is presented in this study. Method and Materials: Using a Varian linear accelerator, dose rate dependence was studied for Kodak films (XV and EDR). The dose rate on this unit could be varied in the range of 80–400 MU/min for both (6 MV and 15 MV) photons beams. A large dose rate range; 5 cGy/min −1100 cGy/min was achieved in conjunction with distance (1–4 meters) and machine dose rate. This was verified using ion chamber. At each dose rate, films were exposed in a solid phantom at a depth of dmax for 300 cGy and 50 cGy for EDR and XV films, respectively. Calibration curves (dose vs. OD) were also established during this experiment in a standard condition. The measured dose through film and ion chamber were compared and analyzed. Results: Reciprocity law holds good in the dose rate range of 20–400 cGy/min for both energies but deviates at low and high dose rates. The effect is more pronounced at dose rate beyond 400 cGy/min where deviation up to 7.5% was noted for both the films. At low dose rate, the deviation is −3.5% for both films and energies. Conclusion: Low and high dose regions are created in the same time of exposure in IMRT and hence reciprocity law becomes critical for film dosimetry. The reciprocity law failure is due to the interaction of ion pairs to form latent image, which could be suppressed at extreme dose rates. The dosimetric impact is noted to be up to 7.5% for both films.

Defects in the silver halide photographic process

The imaging efficiency of today's photographic film and paper is influenced in a variety of ways. Among them, the incorporation of dopants is widely used to increase efficiency, control contrast or improve imaging deficiencies such as reciprocity law failure. Transition metal-organic ligand dopants are attractive because the organic ligand influences the photographic properties. Experimental studies have shown that many of these dopants incorporate well into the silver halide microcrystal even with large organic ligands. In this paper, experimental and computational results are presented on a variety of Ir-OL dopants in AgCl where OL is a small nitrogen and/or sulfur-containing heterocycle. Electron paramagnetic resonance methods provide information about the electronic structure, electron trapping properties and the stability of the electron trap state. These results are complemented by ab initio studies that give information about the optimum structure, charge compensation and the possibility of electron and hole trapping.

Extended focal-film distance technique: an analysis of the factors in dose reduction for the AP knee radiograph

Purpose : While an increase in focal film distance (FFD) is an effective method of reducing the entrance skin dose received by a patient, the literature is not agreed on the principal factors involved. Past work has suggested that the reasons for dose reductions may include geometric factors, air attenuation, reciprocity law failure, extra focal radiation, changes in the scatter to primary radiation ratio (s/p) and back-scatter factor variations. This diversity of opinion can lead to confusion when the technique is applied to other areas of skeletal radiography, and hence is investigated in this paper.Method : The effect of increasing FFD from 100cm to 176cm was investigated for a non-Bucky knee radiograph. A 16.2cm thick anthropomorphic knee phantom was radiographed at 60kVp with the mAs varied to give a constant density on the radiograph. Steel ball bearings were taped to the phantom surface to calculate s/p on the resulting radiographs. Dose measurements were made both with and without the phantom present allowing the backscatter factor to be calculated for both varying FFD and collimator settings. Air attenuation measurements were calculated using a computer programme.Results : Results showed that the skin dose reduction was 13.4% at 176cm FFD with 0.8% due to extra focal radiation variations. This compares to 14.8% (theoretically calculated due to geometric considerations alone) with 3.5% calculated to be due to air attenuation. No variations in s/p and backscatter factor were measured.Conclusions : Geometric factors are the main factors in dose reduction with increasing FFD. Caution is urged when extending this technique to include a grid, as grid-focus decentring would be expected to lessen dose reduction.

Image quality and dose in film-screen magnification mammography.

Extended exposure times in magnification mammography are a result of the reduced X-ray tube currents required for a small focal spot. The consequences of this are the potential for reduced image quality through motion blur during exposure as well as the onset of film reciprocity law failure. Previous investigators have suggested increasing the X-ray tube potential as a practical mechanism for reducing exposure times in magnification mammography and have demonstrated negligible image quality degradation at least up to 32 kVp. This paper describes a film-screen magnification mammography study that expands upon this previous work to investigate the magnitude of the reduction of breast mean glandular dose and exposure time and the changes in subjective image quality (visibility of low contrast details in an RMI 152 phantom) with increases in tube potential between 28 kVp and 35 kVp. Measures of changes in the radiographic contrast and in the scatter-to-primary ratio (SPR) in magnification geometry as a function of tube potential were also obtained. Evidence for reciprocity law failure was also assessed. For a constant film optical density, increasing the X-ray tube potential from 28 kVp to 35 kVp reduced the mean glandular dose from 3.9 mGy to 2.7 mGy and reduced the exposure time from 3.2 s to 1.0 s. Over this range, the detection rate of fibrils and microcalcification-mimicking specks did not vary with tube potential at the 0.05 level of significance. It was found that only the low contrast mass detail detection rate at 35 kVp was significantly less than that at 28 kVp. The measured radiographic contrast decreased with tube potential and the SPR increased with tube potential. However, both changes were weak, and linear regressions determined that the 95% confidence intervals of the slopes relating both contrast and SPR with tube potential encompassed zero. It is concluded that magnification mammography performed at 34 kVp yields significant reductions in exposure time and mean glandular dose, with a detail detection capability similar to that at 28 kVp.

Influence of the Oxygen Partial Pressure on the Photo-Curing of Photo-Oxidation Induced Polycondensation Resin.

The unique properties of the photo-oxidation induced polycondensation resin (POP resin) were experimentally investigated using 1H NMR analysis, photolithographic evaluation and photo-DSC analysis. While a conventional photo-radial polymerization (PRP) type resin showed the phenomenon of reciprocity law failure at low intensity irradiation and decreasing thickness of the developed film with increased oxygen partial pressure, oxygen was found to improve the sensitivity of the POP resin Post-exposure baking (PEB) also enhanced the curing of the POP resin. The 1H NMR study indicated that the precursor at the crosslinking point is relatively stable at room temperature. The effectiveness of C60, added to the POP resin was discussed on the basis of the photo-DSC analysis.

Characterization of the reciprocity law failure in three mammography screen-film systems.

The purpose of this project was to quantify reciprocity law failure (RLF) for mammography screen-film systems. Three widely used screen-film systems were evaluated: the Kodak MinR 2000 system. Fuji UM Mammo Fine screen and Fuji UM MA HC film, and Agfa MR Detail screen and Agfa Mammoray MR5 film. The logit algorithm that linearizes logistic curve shapes was utilized to characterize film sensitometric response. Different values of mammographic phantom thickness, tube current, and kVp were used to vary screen-film exposure rates. RLF was quantified by examining the dependence of logit parameters (maximum and minimum film density, curve shift, and slope) on exposure rate. The shift of the logit curve was found to be a good indicator of the screen-film system speed, while the slope of the logit curve is affected by the RLF. RLF leads to changes in film contrast as well as speed. For the range of exposure rates measured (50-fold), screen-film contrast and speed varied by factors of 2 and 3.5, respectively. Film contrast decreased as exposure rate increased. The greatest changes were observed with the Kodak MinR 2000 screen-film system.

High-Intensity Fluorescent Light-Fading Tests for Digital Output Materials

Digital hard copy output has increased dramatically as an alternative to traditional imaging systems. From family pictures output by home computers to commercial signage and art reproduction, companies are rushing to get a piece of the digital pie. At first, the problems of resolution, printing technology, color reproduction and digital capture were the center of attention. With advances in solving these issues and the resulting increase in demand for the new products come new questions. A customer will marvel at the ease of use, the acceptable image quality and speed of editing, but now that same customer will ask, “How long is it going to last?”.In the digital world, new output technology, new ink sets for existing devices and new media are appearing every day. With these developments comes the need to reassure the consumer that the new products will have a usable life adequate to the proposed application. In traditional photography, there is a battery of accelerated tests to compare and predict life expectancy of both the image and the support. Until now, tests of digital hard copy materials have had to rely on the precedents established by the photo industry. The Image Permanence Institute has constructed a high-intensity (50 to 100 klx) fluorescent light-fading apparatus aimed at giving fast answers to questions about display life of digital hard copy output images. After comparative tests at different light intensities, it has been determined that some inkjet materials do not suffer from reciprocity law failure common to photographic materials. This means that high-intensity, short-term tests can be a reliable indicator of long-term stability in these materials.

Control of Medical X-Ray Film Processing by Light Sensitometry: the Influence of Reciprocity Law Failure and Intermittency Effect

In medical X-ray imaging, film processing is one of the main parameters determining image quality, An important method for controlling film processing is sensitometry. Light sensitometers in which electroluminescent foils serve as light sources are widely used for this purpose. These sensitometers emit light pulse trains of different pulse repetition frequency and different total length, which may cause intermittency effects or give rise to reciprocity law failure. These effects may increase the uncertainty of this sensitometric method to an extent which is no longer tolerable for the intended purpose. The effects were measured for a great number of films of five leading film manufacturers. The results are presented and steps proposed which should be taken to make this kind of sensitometry more reliable.

25 乳房撮影システムにおける相反則不軌と写真特性について

25 乳房撮影システムにおける相反則不軌と写真特性について

Effects of Crossover and Low-intensity Reciprocity Law Failure on LSF

Effects of Crossover and Low-intensity Reciprocity Law Failure on LSF

Holographic 4x4 star-coupler in silver-halide sensitized gelatin

Star couplers are fanin-fanout devices with each input beam split into several output beams with arbitrary intensities traveling at different angles. We demonstrate a 4 x 4 holographic star coupler fabricated as multiplexed holographic gratings in silver-halide sensitized gelatin (SHSG) derived from Agfa-Gevaert plates. The processing formula is modified to achieve high diffraction efficiency and an acceptable modulation transfer function within the region of spatial frequencies of interest. The holographic characteristics of the processed SHSG are measured. The required gratings are recorded simultaneously to avoid reciprocity law failure, which occurs in SHSG as well. The gratings are recorded to ensure equal grating strength, which gives an acceptable intensity ratio between the output beams. The star coupler is examined for use as a broadcast medium in fiber-based local area networks (LAN5), where relatively high loss and inhomogeneity between the outputs could be tolerated.

Holographic Optical Beam Splitters in Dichromated Gelatin

Abstract Holographic beam splitters can split an incoming beam into several partial beams travelling at different angles with arbitrary intensities, thus offering high design flexibility. In this paper the fabrication of beam splitters as multiplex holograms in dichromated gelatin is reported. Shrinking or swelling of the gelatin was avoided by careful process control, reciprocity law failure (as expected from silver halide holograms) was not observed, and, for example, a 1 : 2 beam splitter diffracting 47·4% and 47·0% of the incoming light into two higher orders was realized.

Increased radiation dose at mammography due to prolonged exposure, delayed processing, and increased film darkening.

Four single-emulsion films introduced over the past 2 years--Du Pont Microvision, Fuji MiMa, Konica CM, and Eastman Kodak OM--were compared with Eastman Kodak OM SO-177 (Min-RE) film to evaluate their varying effects on mean glandular dose of reciprocity law failure due to prolonged exposure, delayed processing, and increased film darkening as a result of increased radiation exposure to improve penetration of glandular tissue. Exposures over 1.3 seconds led to increased radiation doses of 20%-30%. Delays in processing of 6 hours decreased processing speed by 11%-32% for all films except Du Pont Microvision. Optical density increases of 0.40 required 20%-30% more skin exposure for all five films. Optimal viewing densities were also evaluated and found to be different for each of the five films. Mammographers need to be aware of these differences in mammographic films to achieve maximum contrast at mammography.

Measurement of the diffraction efficiency of individual images in multiplexed holography

It is important in multiplex holography to measure the relative and absolute diffraction efficiencies of the individual images because of the phenomenon of holographic reciprocity law failure (HRLF). Existing techniques based on diffraction grating images cannot be used for realistic multiplex holograms. This paper describes a simple and rapid technique, based on a charge-coupled device (CCD) camera and digital oscilloscope, that can be applied to all multiplex holograms where the images are spatially separated. Both absolute and relative diffraction efficiencies can be measured, and by using an image area comparison technique some insensitivity to focusing errors is obtained.

Logistic representation of the sensitometric response of screen–film systems: Empirical validation

An empirical logistic model that linearizes the sensitometric response data of screen-film systems over the entire dynamic range of exposures is presented. This linearization is evident when the net optical densities are scaled as fractions of the net saturation density and plotted on commercial logit, probit, or double-log paper, except under conditions of reciprocity law failure. Weighted linear regression analysis shows that the intercept, but not the slope, depends on the screen-film system used. Previous work indicates that the slope is also independent of development time and photon energy. The model is verified through an analysis of tabulated sensitometric data published by the Center for Devices and Radiological Health.