Darkroom Environment Research Articles

Quantitative radiation dosimetry by measuring thermoluminescence of resistors in electronic personal dosimeters

A study on retrospective dosimetry was performed using electronic personal dosimeters (EPDs) for reconstructing doses received by radiographic testing workers. The dosimetric properties of the thermoluminescence (TL) peak in the temperature range of 100–200 °C were investigated by measuring the TL of the resistors extracted from the EPDs in a darkroom environment. Results showed that this TL peak exhibited optimal dosimetric properties, with a minimum detectable dose as low as 13 mGy. To calculate the absorbed dose using the resistors, a simplified single aliquot regenerative (SAR) dose method using the TL peak was employed. The zero dose of the commercial EPD (model CLOVER) was determined to be 58 ± 72 mGy through the random selection of six EPDs. Additionally, a dose overestimation correction factor for compensating rapid sensitivity changes after TL measurement of the natural sample was calculated as 1.73 ± 0.09. Furthermore, it was observed that the TL signal faded exponentially to approximately 60% over a period of 12 weeks. Subsequently, retrospective dosimetry was performed by irradiating EPDs with a standard gamma ray dose of 1 Gy. The radiation exposure dose calculated from the TL peak of the resistors was found to be approximately 10% lower. These findings showed that the retrospective dosimetry with EPD can be utilized for accurately estimating the radiation exposure dose.

Improving the performance of speckle correlation imaging by using a speckle refinement method with self-calibrated homomorphic filtering

Scattering imaging based on speckle correlation is an attractive topic as it enables the rapid reconstruction of the object image through computational methods in a compact setup. However, this method typically relies on high-contrast speckle images obtained under narrowband light illumination in a darkroom environment, limiting its application scenarios. Here, we demonstrate a self-calibrated homomorphic filtering (SCHF) method that significantly enhances speckle contrast by modifying the distribution of components within the speckle image, thereby improving imaging performance. The experimental results reveal that our method leverages the physical mechanism of speckle correlation to obtain the optimal filtering solution under the guidance of a self-calibrated strategy. The integration of this method with current mainstream speckle correlation techniques showcases its scalability. Even in scenarios under ambient light interference or broadband light illumination, the SCHF is effective in improving imaging performance, demonstrating its practical application potential.

Near-infrared luminescent properties and applications of Fe3+-doped YAG phosphors

This study employed the high-temperature solid-phase method to successfully synthesize a comprehensive range of Y3Al12O5: xFe3+ novel near-infrared (NIR) phosphors based on yttrium aluminum garnet material. The samples were subjected to characterization utilizing X-ray diffraction (XRD), scanning electron microscopy (SEM), absorption spectroscopy, first-principles calculations, excitation and emission spectroscopy, as well as temperature-dependent luminescence intensity analysis. Subsequently, the specimens were encapsulated within light-emitting diodes (LED) to facilitate their application in night vision and biometric sensing. The results revealed that all sintered samples were phase-pure, with particle sizes around 0.6 μm, exhibiting uniform and fully developed morphology. The absorption spectroscopy indicated a decrease in the bandgap with increasing Fe3+ doping concentration. The first-principles results revealed that the doping of Fe3+ introduces Fe-d orbitals, and their contribution to the conduction bands is nearly comparable to that of the d orbitals of the Y3+. The spectroscopic results indicated that the samples can be excited through charge transfer of O2− → Fe3+, leading to near-infrared emission at 784 nm with a full width at half maximum (FWHM) of 77 nm at 280 nm, and the FWHM is 73 nm under excitation at 411 nm. The thermal stability analysis revealed that as the temperature increased, there was no observed redshift or blueshift in the emission spectra. The encapsulated NIR LED allows clear visibility of blood vessels on the hand and cacti in a dark room environment. All the aforementioned results provide substantial evidence for the significant application potential of Y3Al12O5: xFe3+ NIR phosphors in biometric sensing and night vision.

Digital holography without a dark room environment: extraction of interference fringes byusing deep learning.

When obtaining digital holograms, dark rooms are used to prevent the influence of natural light on the formation of holograms. Further, in recent years, researchers have actively studied machine learning techniques such as deep learning to resolve image-related problems. In this study, we obtained a pair of holograms influenced by natural light and holograms unaffected by natural light, and trained U-Net to perform image transformation to remove the effects of natural light from holograms. Thus, this study aimed to propose a method for eliminating the effects of natural light from holograms by using the U-Net we trained. To verify the effectiveness of the proposed method, we evaluated the image quality of the reconstructed image of holograms before and after image processing by U-Net. The results showed that the peak signal-to-noise ratio (PSNR) increased by 7.38[dB] after processing by U-Net. Additionally, the structural similarity index (SSIM) increased by 0.0453 after processing by U-Net. This study confirmed that in digital holography, holograms can be acquired without the use of a dark room and that the method proposed in this study can eliminate the effects of natural light and produce high-quality reconstructed images.

Customizing ultraviolet curable polymer‐ink properties via reactive diluent modification and viscosity control

AbstractIn inkjet 3D printing, material selection plays a crucial role in shaping both printing performance and material characteristics. Achieving the desired properties relies on precisely formulated compositions. In this context, ultraviolet (UV) curable polymers require specific viscosities, typically ranging from 3700 to 5700 mPa·s, to function effectively in 3D printing's material jetting technique, preventing complications during material dispensing. This study formulates UV‐curable polymers by blending four distinct monomers: Genomer 4247 Aliphatic Urethane Dimethacrylate, 1,10‐Decanediol Dimethacrylate, Isobornyl Acrylate, and Methyl Acrylate, within a controlled dark room environment at room temperature to prevent undesired crosslinking reactions during mixing. The selection of these monomers and their compositions is meticulous, considering their capacity to achieve specified viscosities and enhance overall material performance. This formulation process yields a wide range of UV‐curable polymer viscosities. The study employs comprehensive methodologies, including rheometry, Fourier transform infrared analysis, Soxhlet extraction, thermal analysis, and tensile testing, for rigorous evaluation of viscosity, curing efficiency, thermal characteristics, and mechanical performance. Notably, mechanical and chemical performance exhibits marginal differences within the viscosity range, attributed to UV‐curable polymer crosslinking, consistently exceeding 99% for all samples. However, the polymer composed of 98% v/v oligomer and methyl acrylate (MA) demonstrates notably better thermal and mechanical properties due to its 99.91% gel content crosslinking. Remarkable polymer fabrication thus occurs within the desired viscosity range.

High-Efficiency ZnS: Cu+, Al3+ Scintillator for X-ray Detection in a Non-Darkroom Environment.

Scintillator is a key component in X-ray detectors that determine the performance of the devices. Nevertheless, due to the interference of the ambient light sources, scintillators are only operated in a darkroom environment currently. In this study, we designed a Cu+ and Al3+ co-doped ZnS scintillator (ZnS: Cu+, Al3+) that introduces donor-acceptor (D-A) pairs for X-ray detection. The prepared scintillator displayed an extremely high steady-state light yield (53,000 photons per MeV) upon X-ray irradiation, which is 5.3 times higher than that of the commercial Bi4Ge3O12 (BGO) scintillator, making it possible in X-ray detection with the interference of ambient light. Furthermore, the prepared material was employed as a scintillator to construct an indirect X-ray detector, which performed a superior spatial resolution (≈10.0 lp/mm) as well as persistent stability under visible light interference, demonstrating the feasibility of the scintillator in practical applications. Therefore, this research presented a convenient and useful strategy to realize X-ray detection in a non-darkroom environment.

Quantification of Phycocyanin in Inland Waters through Remote Measurement of Ratios and Shifts in Reflection Spectral Peaks

This study introduces a semi-empirical algorithm to estimate the extent of the phycocyanin (PC) concentration in eutrophic freshwater bodies; this is achieved by studying the reflectance characteristics of the red and near-red spectral regions, especially the shifting of the peak near 700 nm towards longer wavelengths. Spectral measurements in a darkroom environment over the pure-cultured cyanobacteria Microcystis showed that the shift is proportional to the algal biomass. A similar proportional trend was found from extensive field measurement data. The data also showed that the correlation of the magnitude of the shift with the PC concentration was greater than that with chlorophyll-a. This indicates that the characteristic can be a useful index to quantify cyanobacterial biomass. Based on these observations, a new PC algorithm was proposed that uses the remote sensing reflectance of the peak band around 700 nm and the trough band around 620 nm, and the magnitude of the peak shift near 700 nm. The efficacy of the algorithm was tested with 300 sets of field data, and the results were compared to select algorithms for the PC concentration prediction. The new algorithm performed better than the other algorithms with respect to most error indices, especially the mean relative error, indicating that the algorithm can reduce errors when PC concentrations are low. The algorithm was also applied to a hyperspectral dataset obtained through aerial imaging, in order to predict the spatial distribution of the PC concentration in an approximately 86 km long reach of the Nakdong River.

Corneal-Smart Phone: A novel method to intelligently estimate postmortem interval.

The changes of postmortem corneal opacity are often used to roughly estimate the postmortem interval (PMI) in forensic practice. The difficulty associated with this time estimate is the lack of objective means to rapidly quantify postmortem corneal changes in crime scenes. This study constructed a data analysis model of PMI estimation and implemented an intelligent analysis system for examining the sequential changes of postmortem corneal digital images, named Corneal-Smart Phone, which can be used to quickly estimate PMI. The smart phone was used in combination with an attachment device that provided a darkroom environment and a steady light source to capture postmortem corneal images. By segmenting the corneal pupil region images, six color features, Red (R), Green (G), Blue (B), Hue (H), Saturation (S), Brightness (V) and four texture features Contrast (CON), Correlation (COR), Angular Second Moment (ASM), and Homogeneity (HOM), were extracted and correlated with PMI model. The results indicated that CON had the highest correlation with PMI (R2 =0.983). No intra/intersubject variation in CON values were observed (p>0.05). With the increase in ambient temperature or the decrease in humidity, the CON values were increased. PMI prediction error was <3h within 36h postmortem and extended to about 6-8h after 36h postmortem. The correct classification rate of the blind test samples was 82%. Our study provides a method that combines postmortem corneal image acquisition and digital image analysis to enable users to quickly obtain PMI estimation.

Host-to-host TCP/IP connection over serial ports using visible light communication

As the radio spectrum becomes increasingly crowded, the superior spectral capacity in the visible light range becomes increasingly attractive. Visible light communication (VLC) technology uses the light waves from light emitting diode (LED) lamps and overheads to stream data and connect people as a more efficient, more available, and more secure alternative to Wireless Fidelity (Wi-Fi). The aim of this paper is to enable a host-to-host Transmission Control Protocol/Internet Protocol (TCP/IP) connection over serial ports using VLC. The data is transmitted from a serial port to a virtual tunneling device (TUN) so that the processor receives the information without using the Ethernet connection. In order to check the status of network connections between two computers, the ping tool is used. Pinging checks whether it is possible to reach one computer from another. Moreover, frequency dependence of the communication is tested. The setup reached 96% success rate and 239.233 ms average ping time in 41 trials for a 15 cm separation distance between the two transmitter and receiver pairs. Success rate of communication broke down at 70 cm separation distance under a dark room environment. A realistic application scenario of our presented technique would be to connect a computer that has its TUN programmed to provide an Ethernet connection over an optimized LiFi design setup with state-of-the-art characteristics in terms of data rate and power efficiency.

Spectral Library Creation of Garnet in Kadavur Basin, Karur District, Tamil Nadu, India – A Lab-Based Spectral Library Creation

The significance of the study is to create a spectral library for the mineral Garnet. The spectra for Garnet created in the darkroom environment for the study. The laboratory spectra created matched with the USGS spectral library and made confirmation for the spectra. For the spectral resampling and spectral matching, ASTER data used as the reflectance file. The wavelength of the laboratory spectra is between 0.556 to 2.4 micrometres. The highest reflectance spectral curve of the laboratory spectra shows 1.00 reflectance value and the wavelength is 0.807 μm. The USGS spectra also indicate the same value and wavelength. The absorption value changes in lab spectra at 0.57 reflectance value at the wavelength of 1.65 μm. The USGS spectra display 0.506 absorption value at the same wavelength of the laboratory spectra. The USGS spectra of the Garnet shows that the Garnet collected from the study area is Spessartine garnet. The laboratory spectral library thus created can be used for the mineral identification and also the spectral library thus created can use for further studies.

Evaluation of the Effect of Light and Scanning Time Delay on The Image Quality of Intra Oral Photostimulable Phosphor Plates.

Background:Nowadays, digital radiography is widely used in dental practice. One of the most common types is Photo Stimulated Phosphor Plate (PSP).Objective:The aims of this experimental study were to evaluate the impacts of different combinations of storage conditions and varying delays in reading of digital images captured using PSPs.Methods:Standardized images of a step wedges were obtained using PSPs from the Digora digital systems. Plates were exposed and immediately scanned to produce the baseline gold standard. The plates were re-exposed and stored in four different storage conditions: white light, yellow light, natural light environment and dark room, then scanned after 10 and 30 minutes and 4 and 8 hours. Objective analysis was conducted by density measurements and the data were analyzed statistically using GEE test. Subjective analysis was performed by two oral and maxillofacial radiologists and the results were analyzed using McNemar’s test.Results:The results from GEE analysis show that in the natural light environment, the densities in 10 minutes did not differ from the baseline. The mean densities decreased significantly during the time in all environments. The mean densities in step 2 for the dark room environment decreased with a slighter slope in comparison to yellow environment significantly.Conclusion:PSP images showed significant decrease in the density in plates scanned for 10 minutes or longer after exposure which may not be detected clinically. The yellow light environment had a different impact on the quality of PSP images. The spatial resolution did not change significantly with time.

Fiber optic SPR sensor for liquid concentration measurement

A novel chemical method based on silver mirror reaction is proposed to fabricate the optic fiber surface plasmon resonance sensing probe for liquid concentration measurement. Compared to traditional physical methods, this chemical method is more convenient, resources conservation and inexpensive. And it does not need any complicated equipment. A liquid concentration measurement system with end-reflection optic fiber SPR sensor was set up. Then the comparison experiment between darkroom environment and natural light environment was conducted. As a result, the effect from natural light was eliminated. Glycerol solutions with different volume concentrations (from 0% to 50%) were measured, and the shifts in resonance wavelength were obtained. The sensitivity of the sensor is found to range from 346.7nm/% to 890.7nm/%.

Automatic Recognition of Hub Classification Based on Machine Vision

Based on machine vision principle, automatic recognition system is advanced to distinguish hub classification with different types. Firstly, the dark room environment is set up to eliminate the environmental interference. Secondly, the height of automobile hub is obtained with the grating ruler, and the diameter of automobile hub is achieved through image contours analysis. Finally, hub classification is accomplished through the Hu moment analysis of hub holes. Experiments show that the system can meet the needs of recognition online for hub classification, which can improve productivity effectively, and is of great application value.

Research on radiometric calibration for super wide-angle staring infrared imaging system

To perform radiometric calibration on super wide-angle staring infrared imaging system, the calibration experiment is carried out by using a standard blackbody source with a plate shape in laboratory, and the error analysis and data inversion are made based on the calibration results. Firstly, through analyzing the influencing factors including optical system, detector and signal processing circuit, the optical response model is established. Then, the radiometric calibration experiment is developed in the darkroom environment, and the error analysis is done from six aspects, which are the temperature and radiation instability of the black body, goniometer accuracy, angular resolution, the instability of detector output, data fitting error. Finally, according to the calibration results and the imaging characteristics of short-range airplane in the system, the infrared radiation intensity of aircraft target is calculated. The radiometric calibration and data inversion will benefit obtaining the target radiation characteristic during the system application, and can provide data reference for target detection, recognition, classification, so on.

암순응 환경에서 조도수준과 표적크기가 탐지시간에 미치는 영향

Effects of dark adaptation have large safety implications. This study was aimed to investigate the effects of varying illuminance and the size of critical detail on visual performance (i.e., time-to-detect) in a dark room environment. While adapting to the dark environment, ten subjects were asked to detect and answer simple numerical expressions under 9 experimental conditions (3 illuminance level × 3 target size). The ANOVA results revealed that the time-to-detect was significantly affected by both of the illumination level and the size of critical detail. As illumination increased from 10 lux to 20 lux, the time-to-detect was significantly declined. For the size of critical detail, 0.5/min size (i.e., equal to 2 minutes of visual angle) resulted in a shorter time-to-detect, as compared to 0.7/min size (i.e., equal to 1.6 minutes of visual angle). Potential applications of this research include the development of design guidelines for illumination and warning signs in poorly illuminated viewing environments.

Assessment of safelight handling times in darkrooms: A novel paradigm

Background Safelight illumination should give enough visibility for the technician in the darkroom to handle and process film whilst resulting in minimum detrimental effect to unprocessed film. Safelight handling times (maximum time for which a film can be exposed to safelights without any appreciable degree of fogging) should always exceed film handling times. Previous workers have not considered this relationship. This investigation therefore is aimed to specifically measure and define the safelight handling time and film handling time in seven Dublin hospitals. Causal agents for unacceptable safelight handling times were sought. Method A modified version of the safelight handling test described in the ISO-8374 (2001) E-Determination of Safelight Conditions was used. This consisted of a pre-exposed film held in a darkroom environment under increasing times of safelight exposure. Image densities were measured and a safelight handling time was established. The film handling time was determined by recording the mean time taken for each technician in each darkroom to handle film, over a 2-h period. A safelight handling time to film handling time ratio was calculated. Technical information of safelights and darkrooms were recorded for each hospital. Results and recommendations Safelight and film handling time measurements demonstrated that only three of the seven hospitals tested were operating under appropriate lighting conditions. The maximum mean film handling time noted was 28 s, indicating that a minimum safelight handling time of at least 30 s is needed in darkrooms. Working area light levels were found to have a significant relationship with safelight handling time and a working area light level of 1.8 lx should facilitate acceptable safelight handling times. The authors present the novel approach described in the work as an effective way of monitoring darkroom safelight conditions.

Physician diagnosed asthma, respiratory symptoms, and associations with workplace tasks among radiographers in Ontario, Canada

Background: Medical radiation technologists (MRTs) or radiographers have potential exposure to chemicals including sensitisers and irritants such as glutaraldehyde, formaldehyde, sulphur dioxide, and acetic acid. Aims: To determine the prevalence...

Radiograph quality evaluation for exposure variables--a review.

Good quality radiographs are essential for making accurate diagnoses. Many factors influence the quality of radiographs including the x-ray machine specifications and settings, the darkroom environment and processing, and the choice of ancillary x-ray equipment (cassette properties, film/screen selection, use and properties of a grid). In compiling a technique chart, many of these variables are standardized so as to provide dependable guidelines for selecting the appropriate exposure settings (mAs and kVp) for a radiographic study. The systematic evaluation of image blackening, peripheral blackening, and the visibility of the gross image detail and contrast will facilitate the development of a technique chart as well as determining the source of the problem and necessary exposure setting changes for radiographs that are suboptimal. A flow diagram is described that will assist with the systematic evaluation of radiographic quality and provide guidelines for correcting exposure errors.

3D Profile measurement using a multi-gray scale compared with reference projections

Using a three dimensional measurement system with a gray code projection, this paper proposes a novel technique for improving the reliability of the space encoding method. This space encoding method can measure a colored object under a normal illuminated environment. The measurement space is separated into 256 sub-spaces by four gray level patterns. These patterns are projected by a liquid crystal display projector, and are observed by a CCD camera. When the measurement area is 160 mm × 130 mm, the measurement accuracy of this system is approximately 0.5 mm, and the standard deviation is 0.35 mm in a dark room environment and 0.39 mm in a normal illuminated environment. It is shown that this method can be used to measure a colored object by measuring a colored plaster figure in a dark room environment and under a normal illuminated environment.

Prolongation of a visual afterimage with systematic alternation of room illumination

The present study investigated the effect of changing room illumination on perceived afterimage duration. Subjects observed a light pulse and reported upon their perception of a resultant afterimage. This afterimage was first produced and observed in the dark and was continually viewed in this environment until it was reported to have disappeared. The room lights were then turned on, and the subjects reported if the afterimage reappeared and, if it did, on its persistence. Upon the afterimage’s disappearance in the lighted environment, the room lights were turned off and, again, subjects reported upon the afterimage. This systematic alternation between dark and light room environment continued until subjects no longer reported perceiving an afterimage. It was found that such alternation prolonged afterimage duration, with four illumination changes appearing to be the maximal number for producing the effect.