Digital Single-lens Reflex Camera Research Articles

Versatile luminescence thermometry via intense green defect emission from an infrared-pumped fluorosilicate optical fiber

An all-glass optical fiber capable of two distinct methods of optical thermometry is described. Specifically, a silica-clad, barium fluorosilicate glass core fiber, when pumped in the infrared, exhibits visibly intense green defect luminescence whose intensity and upper-state lifetime are strong functions of temperature. Intensity-based optical thermometry over the range from 25°C to 130°C is demonstrated, while a lifetime-based temperature sensitivity is shown from 25°C to 100°C. Time-domain measurements yield a relative sensitivity of 2.85%K−1 at 373 K (100°C). A proof-of-concept distributed sensor system using a commercial digital single-lens reflex camera is presented, resulting in a measured maximum relative sensitivity of 1.13%K−1 at 368 K (95°C). The sensing system described herein stands as a new blueprint for defect-based luminescence thermometry that takes advantage of pre-existing and relatively inexpensive optical components, and allows for the use of standard cameras or simply direct human observation.

A Preliminary Evaluation of the Diagnostic Performance of a Smartphone-Based Machine Learning-Assisted System for Evaluation of Clinical Activity Score in Digital Images of Thyroid-Associated Orbitopathy.

Background: We previously developed a machine learning (ML)-assisted system for predicting the clinical activity score (CAS) in thyroid-associated orbitopathy (TAO) using digital facial images taken by a digital single-lens reflex camera in a studio setting. In this study, we aimed to apply this system to smartphones and detect active TAO (CAS ≥3) using facial images captured by smartphone cameras. We evaluated the performance of our system on various smartphone models and compared it with the performance of ophthalmologists with varying clinical experience. Methods: We applied the preexisting ML architecture to classify photos taken with smartphones (Galaxy S21 Ultra, iPhone 12 pro, iPhone 11, iPhone SE 2020, Galaxy M20, and Galaxy A21S). The performance was evaluated with smartphone-captured images from 100 patients with TAO. Three ophthalmology residents, three general ophthalmologists with <5 years of clinical experience, and three oculoplastic specialists independently interpreted the same set of images taken under a studio environment and compared their results with those generated by the smartphone-based ML-assisted system. Reference CAS was determined by a consensus of three oculoplastic specialists. Results: Active TAO (CAS ≥3) was identified in 28 patients. Smartphone model used in capturing facial images influenced active TAO detection performance (F1 score 0.59-0.72). The smartphone-based system showed 74.5% sensitivity, 84.8% specificity, and F1 score 0.70 on top three smartphones. On images from all six smartphones, average sensitivity, specificity, and F1 score were 71.4%, 81.6%, and 0.66, respectively. Ophthalmology residents' values were 69.1%, 55.1%, and 0.46. General ophthalmologists' values were 61.9%, 79.6%, and 0.55. Oculoplastic specialists' values were 73.8%, 90.7%, and 0.75. This smartphone-based ML-assisted system predicted CAS within 1 point of reference CAS in 90.7% using facial images from smartphones. Conclusions: Our smartphone-based ML-assisted system shows reasonable accuracy in detecting active TAO, comparable with oculoplastic specialists and outperforming residents and general ophthalmologists. It may enable reliable self-monitoring for disease activity, but confirmatory research is needed for clinical application.

Recognition performance of different artificial neural networks for distinguishing banana slices subjected to different combinations of pretreatment and microwave drying

This study was aimed at assessing the effect of microwave drying at 100, 200, or 300 W on the quality of Cavendish banana slices without pretreatment and with pretreatment using 5% ascorbic acid solution, 5% citric acid solution, 5% gum arabic solution, and ultrasound. Banana slices were imaged using a digital single-lens reflex (SLR) camera. The acquired images were processed to extract texture parameters. The classification models were developed based on image texture parameters selected from a big dataset of 2172 textures of images in different color channels using artificial neural networks. Wide Neural Network, Bilayered Neural Network, Medium Neural Network and three classifiers from the group of function, such as RBF (Radial basis function) Network, Multilayer Perceptron, and WiSARD were applied. Banana slices belonging to 15 classes with different combinations of pretreatment and microwave drying were distinguished with an average accuracy of up to 97.2% for a model built using Multilayer Perceptron. For most models, banana samples microwave-dried at 200 W without pretreatment were classified with the highest correctness. The performed study revealed that the objective, non-destructive, correct, and robust quality assessment of pretreated and microwave-dried banana slices may be performed using image processing and artificial intelligence.

Photogrammetry: Adding Another Dimension to Virtual Gross Pathology Teaching

Pathology is a discipline that relies on the description and interpretation of changes occurring in organs and tissues, and it is largely a “hands-on” experience, both during training and professional practice. Instigated by the need to provide a solution for online learning and teaching, a plethora of different approaches have been tested during the Covid-19 pandemic. The enforced inability to meet in person created the necessity to quickly replace the hands-on experience of practical classes, routinely considered the “gold standard” in undergraduate pathology teaching, with alternative and innovative digital solutions that could allow the students to appreciate most, if not all, features of the specimen to describe and interpret. Here we present a successful deployment of photogrammetry for the purpose of teaching gross veterinary pathology to undergraduate students. Fresh specimens obtained during routine diagnostic post-mortem activity have been photographed using Digital Single-Lens Reflex cameras and rendered into high quality 3D models, preserving almost unaltered morphology, color, and texture, when compared to the original specimen. Once processed using photogrammetry software, exported and uploaded into an online repository, 3D models become readily available via our digital learning platform (CANVAS) to all undergraduate students for self-study and consolidation, as well as to teaching staff for use during online lectures, traditional face-to-face classes, small group teaching and seminars. Preliminary data collected from students’ feedback highlighted the positive reception from users, and the enriched learning experience, while prolonging indefinitely the availability of rare and perishable teaching material.

Enhancing RAW-to-sRGB with Decoupled Style Structure in Fourier Domain

RAW to sRGB mapping, which aims to convert RAW images from smartphones into RGB form equivalent to that of Digital Single-Lens Reflex (DSLR) cameras, has become an important area of research. However, current methods often ignore the difference between cell phone RAW images and DSLR camera RGB images, a difference that goes beyond the color matrix and extends to spatial structure due to resolution variations. Recent methods directly rebuild color mapping and spatial structure via shared deep representation, limiting optimal performance. Inspired by Image Signal Processing (ISP) pipeline, which distinguishes image restoration and enhancement, we present a novel Neural ISP framework, named FourierISP. This approach breaks the image down into style and structure within the frequency domain, allowing for independent optimization. FourierISP is comprised of three subnetworks: Phase Enhance Subnet for structural refinement, Amplitude Refine Subnet for color learning, and Color Adaptation Subnet for blending them in a smooth manner. This approach sharpens both color and structure, and extensive evaluations across varied datasets confirm that our approach realizes state-of-the-art results. Code will be available at https://github.com/alexhe101/FourierISP.

Accreditation of the handheld 3-dimensional scanner and conventional photo images for area measurement.

Accurate assessment of wound areas is crucial in making therapeutic decisions, as the prognosis and changes in the size of the wound over time play a significant role. An ideal assessment method should possess qualities such as speed, affordability, accuracy, user-friendliness for both patients and healthcare professionals, and suitability for daily clinical practice. This study aims to introduce a handheld 3-dimensional (3D) scanner and evaluate its accuracy in measuring wound areas. Engineers from the Industrial Technology Research Institute in Taiwan developed a handheld 3D scanner with the intention of extending its application to the medical field. A project was conducted to validate the accuracy of this 3D scanner. We utilized a smartphone (Asus ZenFone 2 with a 13-million-pixel rear camera), a digital single-lens reflex digital camera (Nikon, D5000, Tokyo, Japan), and the 3D scanner to repeatedly measure square papers of known size that were affixed to the curved surface of life-size facial mask or medical teaching breast models. The "Image J" software was employed for 2-dimensional image measurements, while the "3D Edit" software was used to assess the "area of interest" on 3D objects. By using square papers with predetermined dimensions, the measurement-associated error rate (ER) could be calculated for each image. Three repeated measurements were performed using the "Image J" software for each square paper. The ERs of the 3D scan images were all below 3%, with an average ER of 1.64% in this study. The close-up mode of the smartphone exhibited the highest ER. It was observed that as the area increased, the ER also increased in the digital single-lens reflex camera group. The extension distortion effect caused by the wide-angle lens on the smartphone may increase the ER. However, the definition of a healthy skin edge may vary, and different algorithms for calculating the measurement area are employed in various 3D measurement software. Therefore, further validation of their accuracy for medical purposes is necessary. Effective communication with software engineers and discussions on meeting clinical requirements are crucial steps in enhancing the functionality of the 3D scanner.

Intermittent cryogen spray cooling coupled with cold air jet for heat transfer enhancement and cryogen saving of laser dermatology

Laser dermatology has become a convenient technique for medical treatment. However, the epidermal temperature could be increased, leading to intolerable side effects. Cryogen spray cooling (CSC) is implemented to decrease epidermal damage, but the current CSC could increase cryogen wastage. In this study, the CSC is coupled with a cold air jet (CAJ) and is further subjected to intermittent strategy (ICSC) to mitigate film deposition, enhance heat transfer, and save cryogen consumption, through CAJ-to-spray interaction. The surface temperature is measured by a thin film type-T thermocouple, while the heat transfer is estimated by enhanced Duhamel theorem. The film intensity is captured by a digital single-lens reflex camera through the scattering-illumination technique. The results affirmed the benefits of using ICSC/ICSC-CAJ for laser dermatology. It demonstrated lower surface temperature, film intensity, and film resistance as well as higher convection and efficiency compared with CSC. ICSC-CAJ showed the lowest minimum temperature (1.8%–4.9% decrement) and film resistance (3.8%–17.5% decrement), the highest average convective coefficient (84%–92% increment) and efficiency (7%–9% increment) compared with ICSC. Lower frequency and moderate duties would be preferable for ICSC, while higher frequency and lower duties would be preferable for ICSC-CAJ. The efficiency increased with the saving (110% increment), which insights into our understanding of alternative enhancement toward cryogen saving strategy.

Utility of intraoral scanner imaging for dental plaque detection.

Oral hygiene, maintained through plaque control, helps prevent periodontal disease and dental caries. This study was conducted to examine the accuracy of plaque detection with an intraoral scanner (IOS) compared to images captured with an optical camera. To examine the effect of color tone, artificial tooth resin samples were stained red, blue, and green, after which images were acquired with a digital single-lens reflex (DSLR) camera and an IOS device. Stained surface ratios were then determined and compared. Additionally, the deviation rate of the IOS relative to the DSLR camera was computed for each color. In the clinical study, following plaque staining with red disclosing solution, the staining was captured by the DSLR and IOS devices, and the stained area on each image was measured. The stained surface ratios did not differ significantly between DSLR and IOS images for any color group. Additionally, the deviation rate did not vary significantly across colors. In the clinical test, the stained plaque appeared slightly lighter in color, and the delineation of the stained areas less distinct, on the IOS compared to the DSLR images. However, the stained surface ratio was significantly higher in the IOS than in the DSLR group. When employing IOS with dental plaque staining, the impact of color was minimal, suggesting that the traditional red stain remains suitable for plaque detection. IOS images appeared relatively blurred and enlarged relative to the true state of the teeth, due to inferior sharpness compared to camera images.

Angular Photogrammetric Analysis for a Young Adult Garhwali Population

Abstract Objectives: The aim of this study is to quantify the average parameters that define the soft-tissue facial profile of a young adult Garhwali population of age 18–21 by means of angular measurement on standardized photographs. Materials and Methods: A sample of 50 Garhwali individuals (25 males and 25 females) between 18 and 21 years of age was obtained with a class I dental relationship. The photographic set-up consisted of a tripod that held a digital SLR camera. The photographic records of the subjects were taken in natural head posture. The obtained records were digitized and analyzed using the Digimizer software program. Twelve measurements were digitally analyzed on each photograph. For statistical evaluation, Student’s-t-test was performed and reliability of the method was analyzed. The results were compared with established soft-tissue profile photogrammetric norms. Results: The Student’s t-test was applied to all variables to determine the influence of sex in the measurements. Two of the angles showed sexual differences: nasofrontal (G–N–Prn, P = 0.001) and mentolabial angle (Li–Sm–Pg, P = 0.002). Nasofrontal angle was found wider in the females while mentolabial angle was found be wider in the males. Conclusion: Orthodontist has the ability to alter facial features and must analyze the soft-tissue facial profile and compare it with standard measurements of the soft- tissue facial profile. The sample’s mean values can be compared against records of participants using the same photogrammetric technique and sharing the same attributes. The results showed sexual differences in two of the measurements: the nasofrontal and mentolabial angle.

Accuracy, acceptability and feasibility of photography for use in trachoma surveys: a mixed methods study in Tanzania.

Photography could be used to train individuals to diagnose trachomatous inflammation-follicular (TF) as trachoma prevalence decreases and to ensure accurate field TF grading in trachoma prevalence surveys. We compared photograph and field TF grading and determined the acceptability and feasibility of eyelid photography to community members and trachoma survey trainers. A total of 100 children ages 1-9y were examined for TF in two Maasai villages in Tanzania. Two images of the right everted superior tarsal conjunctiva of each child were taken with a smartphone and a digital single-lens reflex (DSLR) camera. Two graders independently graded all photos. Focus group discussions (FGDs) were conducted with community members and Tropical Data trainers. Of 391 photos, one-fifth were discarded as ungradable. Compared with field grading, photo grading consistently underdiagnosed TF. Compared with field grading, DSLR photo grading resulted in a higher prevalence and sensitivity than smartphone photo grading. FGDs indicated that communities and trainers found photography acceptable and preferred smartphones to DSLR in terms of practicalities, but image quality was of paramount importance for trainers. Photography is acceptable and feasible, but further work is needed to ensure high-quality images that enable accurate and consistent grading before being routinely implemented in trachoma surveys.

An In Vitro Comparative Assessment of Shaping Capacity of a Single-File System Over Multiple-File System in Root Canals.

The study's objective was to contrast the two distinct rotary file techniques used to shape mandibular first molars. The investigation involved twenty recently removed mandibular molars. A digital single-lens reflex (DSLR) camera was placed in a fixed position, a muffle block was built, and images of each tooth's three cross sections were obtained. The specimens were split into the following two groups at random: Rotary files from WaveOne were used to prepare group A and Mtwo rotary files were used to prepare group B. At the coronal, middle, and apical thirds of the root canals, WaveOne file system demonstrated improved centering ability compared with the Mtwo file system (P 0.05). When compared to the Mtwo file system, WaveOne file system demonstrated improved centering capabilities and needed significantly less time to build the curved canals.

REMOTE MONITORING OF RADIATION TEST TEMPERATURE REGIME AT A HIGH-CURRENT ELECTRON ACCELERATOR

Methods for evaluating the radiation resistance of structural materials of nuclear reactors have been developed and research is being carried out in NSC KIPT. As a part of these studies, a supercritical water convection loop with a chamber for irradiation of the tested samples by electron beam of the accelerator LU-10 (beam energy of 8…10 MeV, beam power up to 10 kW) was developed. A pyrometric system based on a DSLR camera (Digital Single-Lens Reflex Camera) has been created for the remote continuous non-intrusive control of the surface temperature of the irradiation cell in the range of 350…550°С. The work presents the results of calibration and use of the developed system in the conditions of a 500-hour run of sample irradiation in the loop.

Comparing image quality and trachoma detection across three camera types from a survey in Kongwa, Tanzania.

There is an increasing demand for photography for trachoma prevalence surveys. In previous studies, digital single lens reflex (DSLR) images were superior to smartphone images, but newer-model smartphones and/or lens attachments may be able to bridge this gap. This study compares the image quality and ability to detect trachomatous inflammation - follicular (TF) of three camera types: a DSLR Nikon camera, an iPhone SE and an iPhone 13 Pro with a cell scope. We surveyed 62 children ages 1-7y from two Tanzanian communities. Upper tarsal conjunctiva images of both eyes were graded for TF by two standardized graders. The McNemar's test and a logistic regression model were used for analyses. The DSLR camera malfunctioned during the study, thus the iPhone SE and iPhone 13 Pro with cell scope were both more likely to take high-quality, gradable photographs (88% and 86%, respectively) compared with the DSLR camera (69%) (p<0.001 and p=0.02, respectively). TF was detected in gradable images from the iPhone SE (8.8%) and iPhone 13 Pro with cell scope (9.0%) at the same rate (p=1.0) as images from the DSLR camera (9.7%). Smartphones with high-quality image capture, like the iPhone SE/13 Pro, have the potential for use in trachoma surveys if the proportion of gradable images can be improved.

Agreement in quantification of removable prosthesis plaque area coverage using a semi-automated planimetric assessment method

ObjectivesTo determine the agreement of removable dental prosthesis cleanliness as assessed by a semi-automated planimetric method between images captured by a digital single-lens reflex camera (DSLR) and smartphone. MethodsA total of 97 participants with removable prostheses were recruited for the quantification of the prosthesis plaque area coverage. The colour images of stained prosthesis plaque were obtained using both a DSLR camera and a smartphone. The prosthesis plaque area coverage was analysed in two ways: (i) prosthesis cleanliness index (PCI) and (ii) percentage plaque area coverage (PPC). The PPC (continuous data) was converted to the PCI (categorical data) to provide prevalence ordinal scales and the agreements in PCI ratings were determined using weighted Kappa statistics. Agreement of PPC scores was determined through assessing directional, standardised directional, and absolute differences and correlation analyses. ResultsWeighted Kappa values of agreement between PCI categories were excellent (> 0.80) for all comparisons. The mean PPC was 24.79 % as determined by DSLR and 25.37 % as determined by smartphone. There was no statistically significant difference in the means of PPC between the DSLR and smartphone (P = 0.149). The standardised directional difference was 0.15 (‘small’). The mean absolute difference was 2.77. The interclass correlation coefficient was 0.98 (‘excellent’). ConclusionsThis method showed almost perfect agreements and allowed for threshold-based plaque segmentation on the removable prostheses. There was substantial agreement between DSLR and smartphone assessment of prosthesis plaque area coverage as determined by a semi-automated planimetric assessment. Clinical significanceThis semi-automated planimetric assessment method has implications for monitoring removable prosthesis hygiene initiatives by offering a valid, reliable, and quantitative method of assessment with potential use in managed care and community settings.

Quantifying Facial Distortion in Modern Digital Photography.

Advancements in digital cameras and the advent of smartphones have magnified the importance of clinical photography in facial plastic surgery. Here, we aim to examine the effect of different camera types, focal lengths, and distances from subjects on facial distortion. Twelve subjects underwent a series of frontal photographs using a smartphone camera and a full-frame digital single-lens reflex camera. Photos were captured at six distances from the subject. Seven focal lengths were used at each distance for the full-frame camera. Measurements of facial landmarks were made for each photo, with those made at 60 inches using the full-frame camera considered the gold standard and used for comparison. Distortion of facial features using the full-frame camera occurred when photos were captured 8 inches away using short focal lengths. A 12%-19% increase in vertical stretching of the midface occurred when using focal lengths of 24, 35, and 50 mm (p < 0.05 for all). The same features were distorted when a smartphone camera was used at 8 inches (18% increase, p < 0.01) and 12 inches (12% increase, p < 0.03). Distortion of midfacial features using both smartphones and full-frame cameras occurs with short, 'selfie' distances between the camera and subject. 2 Laryngoscope, 134:1234-1238, 2024.

Comparative Analysis of Optical Quality of Monofocal, Enhanced Monofocal, Multifocal, and Extended Depth of Focus Intraocular Lenses: A Mobile Model Eye Study.

To use the revised model eye to observe and compare how the world is perceived by patients with monofocal intraocular lens (IOL), Eyhance, bifocal IOL, and Symfony, and check its performance. The new mobile model eye consists of an artificial cornea, an IOL, a wet cell, an adjustable lens tube, a lens tube, an objective lens, a tube lens, and a digital single-lens reflex camera. We collected photographs of distant buildings and streets at night, videos of the focusing process, and videos of United States Air Force resolution target from 6m to 15 cm and analyzed them quantitatively. In this revised model eye using an objective lens, an artificial cornea similar to the human cornea could be used. Using a digital single-lens reflex camera, high-resolution imaging was possible without an additional computer. Fine focusing was possible using an adjustable lens tube. For monofocal IOL, the contrast modulation was 0.39 at 6m and decreased consistently. It was nearly 0 as the model eye got closer than 1.6m. For Eyhance, the contrast modulation was 0.40 at 6m. It then decreased and increased again. At 1.3 m, it was 0.07 and then decreased again. For Symfony, the contrast modulation was 0.18 at 6m. Symfony showed the characteristics of a bifocal IOL with low add diopter. Halos (234 pixels) were observed around lights, although smaller than those seen with bifocal IOL (432 pixels). We could objectively observe and compare how patients with monofocal IOL, Eyhance, bifocal IOL, and Symfony perceived the world using this revised model eye. Data obtained by this new mobile model eye can be used to help patients select their IOLs before cataract surgeries.

Development and Assessment of a Field-Programmable Gate Array (FPGA)-Based Image Processing (FIP) System for Agricultural Field Monitoring Applications

Field imagery is an effective way to capture the state of the entire field; yet, current field inspection approaches, when accounting for image resolution and processing speed, using existent imaging systems, do not always enable real-time field inspection. This project involves the innovation of novel technologies by using an FPGA-based image processing (FIP) device that eliminates the technical limitations of the current agricultural imaging services available in the market and will lead to the development of a market-ready service solution. The FIP prototype developed in this study was tested in both a laboratory and outdoor environment by using a digital single-lens reflex (DSLR) camera and web camera, respectively, as the reference system. The FIP system had a high accuracy with a Lin’s concordance correlation coefficient of 0.99 and 0.91 for the DLSR and web camera reference system, respectively. The proposed technology has the potential to provide on-the-spot decisions, which in turn, will improve the compatibility and sustainability of different land-based systems.

Assessing the environmental impacts of product service systems in the digital-devices market: An application of attributional and consequential life cycle assessment

Product Service Systems (PSS) have received increasing attention as a means for realizing a circular economy. Although PSS are expected to help mitigate the causes of climate change and slow the consumption of scarce natural resources, there is a risk of unintended consequences, resulting in a net increase in environmental impact. Despite this possibility, no effective evaluation method for PSS has been devised. In this study, consequential and attributional Life Cycle Assessment (LCA) approaches, combined with a consumer survey, were conducted to quantify the environmental consequences of PSS using a case study of digital camera rental services in Japan. Attributional LCA showed that greenhouse gas (GHG) emissions in the rental scenario would actually increase relative to the emissions in the conventional purchase-only scenario, from 5.22 kg-CO2 eq. to 18.8 kg-CO2 eq. per individual's use of a digital camera for one year in the case of Digital single-lens reflex camera (DSLR) due to package production and delivery transportation. At the same time, rental services showed the possibility of reducing abiotic depletion potential (ADP) compared to conventional purchase, from 0.667 g Sb-eq. to 0.622 g Sb-eq. in the case of DSLR. The survey revealed four consumer segments emerging after the introduction of PSS: camera owners, hybrid users, shifting rental users, and new rental users, each with different environmental implications. Through consequential LCA, the environmental impacts on a countrywide scale were estimated. For example, GHG emissions were projected to increase by approximately 150 %, mainly caused by delivery processes following the broad acceptance of the camera rental services, whereas ADP increased only slightly due to the comparatively small number of devices needed by these services. The approach used in this study, combining consequential LCA with a consumer survey, points to the need for a better service design that addresses the potential of unintended consequences caused by the introduction of PSS well in advance of any large-scale implementation.

Effect of cross-polarization filters on the trueness of colors obtained with a single-lens reflex camera, macro lens, and a ring flash.

To investigate the effect of cross-polarization filters on the colors of shade tabs obtained with a digital single-lens reflex (DSLR) camera, macrolens, and a ring flash. Digital images of four shade tables (1M1, 3L2.5, 3R2.5, and 5M3) from the VITA Toothguide 3D-Master shade guide were taken using a DSLR camera, 100 mm macrolens, and ring flash with two different cross-polarizing filters (Polar_eyes and Filtropolar), and without (Nonpolarizer; n = 7). The CIE L*a*b* color coordinates of digital images were calculated and remeasured with a spectroradiometer (SR). The color differences (ΔE00 ) between the SR and digital images were calculated and analyzed with the two-way analysis of variance (ANOVA) and Tukey HSD test (α = 0.05). ΔE00 values of all test groups were higher than the clinically acceptable threshold (∆E00 > 1.80). While the ∆E00 values of Filtropolar (6.19 ± 0.44) and Polar_eyes (7.82 ± 0.23) groups were significantly higher than the Nonpolarizer (4.69 ± 0.32) for the 1M1 shade tab, ∆E00 value of Polar_eyes (6.23 ± 0.34) was significantly lower than Nonpolarizer (10.71 ± 0.48) group for 5M3 shade tab (p < 0.05). The color-matching results of tested digital photography techniques with and without cross-polarization were unacceptable, compared to a spectroradiometer. While digital photography with Polar_eyes cross-polarizing filter has closer results to the reference device for the low-in-value shade table (5M3), for the high-in-value shade table (1M1), improved results were obtained without a cross-polarizing filter. The cross-polarization filters are increasingly used in dentistry for tooth color communication with digital photography techniques. However, the digital photography techniques with-without cross-polarization filterers should be improved to obtain clinically acceptable color-matching results.

Photogrammetry-Based 3D Textured Point Cloud Models Building and Rock Structure Estimation

Trace lines on the outcrop of a rock mass are usually the primary data source for the estimation of rock structure. It is important to obtain the data of trace lines precisely. Photogrammetry is well suited to finish this task. However, this is mainly conducted by commercial software, and not every researcher has easy access to the method of digital photogrammetry. This study aims to provide researchers with a low-cost method of building a photogrammetry-based textured 3D point cloud model (FMBPM) and display the applicability of the method to estimating the rock structure of rock masses. In the FMBPM, a digital single-lens reflex camera with a prime lens and a total station are the necessary hardware employed to capture images and measure the coordinates of feature points. A coordinate transformation means of converting model coordinates to physical coordinates was introduced. A program for calculating a joint orientation based on the coordinates of inflection points on the trace line of the joint was developed. A section of a rock slope was selected as a case to show the procedures and the practicability of the FMBPM. The textured 3D point cloud model of the rock slope was successfully built, and the rock structure of the rock slope was analyzed using the joint disk model generated based on the trace lines extracted from the point cloud model. The results show that: (1) the precision of the point coordinates of the textured 3D point cloud model could achieve 3.96 mm, taking the data of the total station as the reference; (2) the rock structure of the slope is good, according to the value of the rock quality designation; (3) the new method is applicable in engineering practices.