3D Photography Research Articles

D-VPnet: A network for real-time dominant vanishing point detection in natural scenes

As an important part of linear perspective, vanishing points (VPs) provide useful clues for mapping objects from 2D photos to 3D space. Existing methods are mainly focused on extracting structural features such as lines or contours and then clustering these features to detect VPs. However, these techniques suffer from ambiguous information due to the large number of line segments and contours detected in outdoor environments. In this paper, we present a new convolutional neural network (CNN) to detect dominant VPs in natural scenes, i.e., the Dominant Vanishing Point detection Network (D-VPnet). The key component of our method is the feature line-segment proposal unit (FLPU), which can be directly utilized to predict the location of the dominant VP. Moreover, the model also uses the two main parallel lines as an assistant to determine the position of the dominant VP. The proposed method was tested using a public dataset and a Parallel Line based Vanishing Point (PLVP) dataset. The experimental results suggest that the detection accuracy of our approach outperforms those of state-of-the-art methods under various conditions in real-time, achieving rates of 115 fps.

Soft Tissue Changes After Clockwise Rotation of Maxillo-Mandibular Complex in Class III Patients: Three-Dimensional Stereophotogrammetric Evaluation.

To evaluate the linear, angular, and volumetric changes of soft tissue after clockwise repositioning of the maxillo-mandibular complex in skeletal class III patients using three-dimensional (3D) stereophotogrammetry and to determine the correlation between changes in the skeletal and soft tissue variables. This study included 18 skeletal class III patients who underwent two-jaw surgery; superior impaction and clockwise rotational movement of the maxilla with the rotation center at upper incisors, and setback of the mandible. Lateral cephalograms and 3D photographs taken before and 6 months after surgery were compared. After maxillary impaction of anteriorly 1.7 mm and posteriorly 3.1 mm, and mandibular setback of 8.7 mm, the volume of lower lip and chin region decreased significantly by 33.6 cm3 (13% net change, P < 0.001), while paranasal and upper lip region volume increased by 3.2 cm3 (2%) and 7.2 cm3 (4%), respectively. The clockwise rotation of maxillo-mandibular complex in class III patients significantly reduced lower lip and chin volume with minimal increase in paranasal and upper lip volumes. 3D stereophotogrammetry can provide quantitative evaluation of facial soft tissue volumetric changes.

Quantitative outcomes of endoscopic strip craniectomy for metopic craniosynostosis in children with severe trigonocephaly

To assess intermediate-term (> 3 years) outcomes of endoscopic strip craniectomy with postoperative helmet therapy (ESC + HT) for the treatment of infants with severe trigonocephaly. This retrospective study examined cranial morphology of consecutive patients with severe trigonocephaly treated with minimally invasive ESC + HT. Preoperative and follow-up clinical parameters were collected from patient charts. Interfrontal divergence angle (IFDA), a validated and accurate measure of forehead narrowing, was measured on preoperative CT scans and on preoperative and postoperative 2D photographs. Seven patients (4 male, 3 female) were included with a mean age at surgery of 2.76 months (range 1.8 to 4.1 months) and mean clinical follow-up of 3.71 years (photographic follow-up 2.73 years). The mean operative time was 91.4 min, with a mean estimated blood loss (EBL) of 57.1 ml and mean hospital length of stay of 1.14 days. IFDA improved from 118.8° to 135.9° (p < 0.01), with the mean final measurement falling within normal limits. The head circumference percentile was not significantly changed in follow-up. There was a statistically significant improvement in the inner-to-outer canthal distance ratio (p = 0.01) in follow-up, showing an improvement in hypotelorism. There were no dural tears, CSF leaks, infections, or other significant surgical morbidities, and there were no serious complications related to the use of helmet therapy. All patients achieved excellent aesthetic results judged by photographic comparison. This study demonstrated that patients treated with ESC + HT for metopic craniosynostosis showed measurable and significant improvement in forehead shape. This technique is a safe and effective alternative to more invasive surgical interventions.

One shot 3D photography

3D photography is a new medium that allows viewers to more fully experience a captured moment. In this work, we refer to a 3D photo as one that displays parallax induced by moving the viewpoint (as opposed to a stereo pair with a fixed viewpoint). 3D photos are static in time, like traditional photos, but are displayed with interactive parallax on mobile or desktop screens, as well as on Virtual Reality devices, where viewing it also includes stereo. We present an end-to-end system for creating and viewing 3D photos, and the algorithmic and design choices therein. Our 3D photos are captured in a single shot and processed directly on a mobile device. The method starts by estimating depth from the 2D input image using a new monocular depth estimation network that is optimized for mobile devices. It performs competitively to the state-of-the-art, but has lower latency and peak memory consumption and uses an order of magnitude fewer parameters. The resulting depth is lifted to a layered depth image, and new geometry is synthesized in parallax regions. We synthesize color texture and structures in the parallax regions as well, using an inpainting network, also optimized for mobile devices, on the LDI directly. Finally, we convert the result into a mesh-based representation that can be efficiently transmitted and rendered even on low-end devices and over poor network connections. Altogether, the processing takes just a few seconds on a mobile device, and the result can be instantly viewed and shared. We perform extensive quantitative evaluation to validate our system and compare its new components against the current state-of-the-art.

Three-dimensional anthropometric analysis of eyelid aging among Chinese women

Eyelid morphology is highly susceptible to aging. Previous studies have described the process of eyelid aging in Caucasians; however, anthropometric data describing aging in Chinese eyelids are lacking. Therefore, this study aimed to quantitatively analyze the effect of aging on the eyelids of Chinese women through a three-dimensional (3D) anthropometry. In this prospective, cross-sectional study, 3D photos were captured from 188 healthy Chinese Han women, who were categorized into four age groups. Anthropometric landmarks were identified for the measurement of eyelid parameters, and a unified coordinate system was built into each subject. Linear and angular measurements were computed from the coordinates and were compared between the groups. An age-related decrease was observed in the ocular width, outer canthal width, palpebral fissure height, and multiple angular measurements. This indicated upper eyelid ptosis, which reduced the lateral and superior visual field. Lateral shift of the upper eyelid arc was not observed. The lower eyelid underwent slight elevation with increasing age. Aging rendered the periorbital region esthetically less pleasing, as shown by changes in the multiple proportion indices computed. Furthermore, an intergroup comparison indicated that eyelid aging was accelerated after the age of 40 years among Chinese women. This study used 3D photography to quantitatively analyze how eyelids in Chinese women changed with age. The anthropometric data collected could help with antiaging cosmetic surgery planning and postoperative assessment.

Measuring Differential Volume Using the Subtraction Tool for Three-Dimensional Breast Volumetry: A Proof of Concept Study.

Background. Three-dimensional (3D) photography provides a promising means of breast volumetry. Sources of error using a single-captured surface to calculate breast volume include inaccurate designation of breast boundaries and prediction of the invisible chest wall generated by computer software. An alternative approach is to measure differential volume using subtraction of 2 captured surfaces. Objectives. To explore 3D breast volumetry using the subtraction of superimposed images to calculate differential volume. To assess optimal patient positioning for accurate volumetric assessment. Methods. Known volumes of breast enhancers simulated volumetric changes to the breast (n = 12). 3D photographs were taken (3dMDtorso) with the subject positioned upright at 90° and posteriorly inclined at 30°. Patient position, breathing, distance and camera calibration were standardised. Volumetric analysis was performed using 3dMDvultus software. Results. A statistically significant difference was found between actual volume and measured volumes with subjects positioned at 90° (P < .05). No statistical difference was found at 30° (P = .078), but subsequent Bland–Altman analysis showed evidence of proportional bias (P < .05). There was good correlation between measured and actual volumes in both positions (r = .77 and r = .85, respectively). Univariate analyses showed breast enhancer volumes of 195 mL and 295 mL to incur bias. The coefficient of variation was 5.76% for single observer analysis. Conclusion. Positioning the subject at a 30° posterior incline provides more accurate results from better exposure of the inferior breast. The subtraction tool is a novel method of measuring differential volume. Future studies should explore methodology for application into the clinical setting.

Monitoring skin metastases during immuno‐ and targeted therapy using total‐body 3D photography

Eruptive skin metastases in melanoma are an uncommon manifestation of rapidly progressive, systemic disease1 . Type and kinetics of these lesions have not been analyzed before, because of the rarity of the event and technical restrictions of total-body photography. We present the first sequential total-body 3D photography-based analysis by a VECTRA 360WB imaging system of a melanoma patient suffering from disseminated, spreading skin metastases under treatment with immune checkpoint antibodies and subsequent BRAF/MEK inhibition.In April 2019 a 54-year-old male patient with BRAF V600E-mutated conjunctival melanoma developed pigmented skin (Fig. 1a), brain, pulmonary, and hepatic metastases. In addition to a cerebral stereotactic radiotherapy the patient received four cycles of a combined immunotherapy with ipilimumab (1mg/kg) and pembrolizumab (2mg/kg).

Synthesis of holograms received by a communication channel

A method for the synthesis of holograms that reconstruct a 3D image using two 2D images, including a topographic map of the surface of a 3D object and photographs of the texture of its surface obtained using coherent and incoherent radiation is proposed. The method is suitable for transmitting information about a 3D object via a communication channel at a distance and subsequent synthesis of holograms at a distance from the holography object. It can be used in augmented reality devices, when creating holographic cameras and 3D video cameras, in 3D projectors and microscopes, devices with a synthesized aperture. The proposed method for the remote hologram synthesis is suitable for reproducing 3D holographic images of distant objects at different parts of the electromagnetic spectrum. Examples of 3D image restoration in the infrared spectral range are given. The method is also suitable for the synthesis of holograms in the UV, THz, and even radio range.

Enhancing the Lateral Orbital "C-Angle" With Calcium Hydroxylapatite: An Anatomic and Clinical Study.

Deliberate injection of specific facial subunits may improve aesthetic outcomes in facial rejuvenation. We contend that the lateral orbital area (LOA) is a key anatomic subunit in the perception of eye attractiveness, with a C-shaped distribution of fat contributing to the formation of a distinct angle in the lateral orbit. The aim of this study was to describe the anatomy of the LOA that constitutes the C-shaped angle and to investigate the safety and cosmetic outcomes of nonsurgical enhancement of that area with calcium hydroxylapatite (CaHA). Four injected fresh-frozen cadaver heads were dissected. Twenty patients were enrolled in a prospective clinical study. Participants were seen on the day of injection, and at 2 weeks and 3 months postinjection. Two-dimensional and 3D photographs were analyzed to quantify the volumetric changes between pretreatment and postinjection time points. Secondary outcomes included Global Aesthetic Improvement Scale score and subject satisfaction at 3 months. Cadaver dissections revealed distinct fat compartments and a zone of adhesion forming the C-shaped area around the lateral orbit. In the clinical study, a mean of 1.88 mL of CaHA was injected into each lateral periorbital region. There was 97% and 76% volume retention at 2 weeks and 3 months, respectively, with 70% of patients being "very satisfied" at 3 months. The average Global Aesthetic Improvement Scale rating at 3 months was 3.95. There were no complications. The LOA is a distinct facial subunit that can be enhanced safely by CaHA injection with good cosmetic outcomes. Focusing on the C-angle can improve periorbital aesthetics.

Evaluating the accuracy of hand models obtained from two 3D scanning techniques

The aim of this study was to identify an efficient approach for 3D imaging of hand. The 3D photographs of hand were taken with Gemini structured-light scanning system (SL scanning) and CT scanning. The 3D photographs, average time of scanning and reconstruction were compared between these two indirect techniques. The reliability, reproducibility and accuracy were evaluated in these two indirect techniques and the direct measurement (DM). Statistical differences in the measurements were assessed by 99% probability, with clinical significance at > 0.5 mm. The Gemini structured-light scanning system established a complete and smooth 3D hand photograph with shorter scanning and reconstruction time. Reproducibility of CT scanning and SL scanning methods was better (P < 0.01, both) than the DM, but did not differ significantly from each other (P = 0.462). Of the 19 (31.58%) measurements obtained, 6 showed significant differences (P < 0.01). Significant differences were observed more often for circumference dimensions (5/9, 55.56%) than for length dimensions (1/10, 10%). Mean absolute error (AE) of the 10 subjects was very low for 3D CT (0.29 ± 0.10 mm) and SL scanning (0.30 ± 0.11 mm). Absolute percentage error (APE) was 4.69 ± 2.33% and 4.88 ± 2.22% for 3D CT and SL scanning, respectively. AE for the PIP circumference between the 3rd finger (0.58 mm) and 4th finger (0.53 mm) scan was > 0.5 mm, indicating significant difference between DM and CT scanning at the level of 99% probability. In this study, the Gemini structured-light scanning system not only successfully established a complete and smooth 3D hand photograph, but also shortened the scanning and reconstruction time. Compared to the DM, measurements obtained using the two indirect techniques did not show any statistically or clinically insignificant difference in the values of the remaining 17 of 19 measurements (89.47%). Therefore, either of the two alternative techniques could be used instead of the direct measurement method.

Three-dimensional evaluation of treatment results of the Alt-RAMEC and facemask protocol in growing patients

The aim of this retrospective study was to evaluate the skeletal, dental, and soft tissue effects of the alternating rapid maxillary expansions and constrictions (Alt-RAMEC) protocol combined with afacemask in prepubertal patients. The study group (mean age 9.74 ± 1.46 years) consisted of 20 patients with classIII malocclusion characterized by maxillary retrognathism. They were treated with afacemask for 7months following a 9‑week Alt-RAMEC protocol. Cone-beam computed tomography (CBCT) records and three-dimensional (3D) photographs taken before (T0) and after the protraction and retention period (T1) were evaluated. The study group was compared with awell-matched control group of 16untreated patients (mean age 9.44 ± 0.79years) with the same malocclusion. The records for the control group included cephalometric radiographs and 3D photographs. In the study group, significant forward movements of Apoint (3.49 mm), nasal (2.91 mm) and zygomatic bones were achieved. Intermolar, internasal, and interzygomatic widths increased. Soft tissue points followed the hard tissue movements, apart from band pog. In the control group, A(0.97 mm), B(1.69 mm), Pog, and bpoints presented forward movement. Significant differences were found regarding the forward movement of the maxilla between the groups. The Alt-RAMEC/facemask protocol was effective not only in the maxillary region but also in the midface.

Lower Blepharoplasty Three-Dimensional Volume Assessment after Fat Pad Transposition and Concomitant Fat Grafting.

Lower blepharoplasty is a commonly performed procedure to improve the aesthetic of the lower eyelid and upper midface. Combined fat pad transposition and fat grafting has not been previously studied using three-dimensional (3D) analysis. The aim of the study is to demonstrate the benefits of fat pad transposition with concomitant autologous fat grafting in lower blepharoplasty and to determine quantitative volumetric effects on the tear trough and lower periorbital region using VectraXT 3D imaging and analysis. A retrospective review was performed to identify patients undergoing primary lower blepharoplasty with combined fat pad transposition and fat grafting. The study time period was from September 2017 to March 2019 with a mean 6.5-month postoperative follow-up. This study was performed in a private practice institution (Kovac Cosmetic Center, Oakbrook Terrace, IL). Nine subjects were enrolled in the study with four males and five females. All subjects underwent lower blepharoplasty with combined fat pad transposition and fat grafting without any additional procedures. Preoperative and postoperative photographs were taken with the VectraXT 3D camera system and software. 3D photographs were then compared to assess the volume changes in the periorbital region. The volume in the lower periorbital region was assessed using 3D analysis. All subjects were found to have an increase in volume in the periorbital region. There was a mean volume gain of 2.84 mL on the right and 2.87 mL on the left. There was no statistical difference among volume gains between sides (p = 0.95). Combined fat pad transposition and autologous fat grafting is an effective procedure for improving the tear trough deformity and periorbital area. The use of 3D volume assessment is able to accurately measure and quantify the volume changes of the postoperative results.

Combined microwaves and fractional microablative CO2 laser treatment for postpartum abdominal laxity.

Postpartum abdominal changes represent a major esthetic concern affecting women. As the abdomen stretches during pregnancy and some of the muscles lose tone, there is an increased skin laxity and a loss of abdominal elasticity. As a result, the abdomen becomes saggy. To evaluate the performance of a combined microwaves and fractional microablative CO2 laser treatment for reshaping and improvement of abdomen texture/laxity and striae distensae in postpartum women. Fifteen women (median age 38years) received three monthly abdomen treatments with a new microwaves platform, the ONDA Coolwaves® (DEKA) system, followed by a treatment with fractional microablative CO2 laser (SmartXide2; DEKA) a month thereafter. We followed up each patient's weight and nutritional habits. Outcome was assessed using reproducible circumference and abdominal measurements, digital and 3D photography, the laxity score as well as patient satisfaction index. The overall mean circumferences reduction was 3.6±1.2cm. Significant improvement in skin laxity and tightening was noted by physicians and patients as well as a reduction of striae distensae. Interestingly, as a result of skin remodeling, repositioning of the umbilicus was also demonstrated. Treatments were well tolerated with no side effects. Our data showed a sustainable reduction in circumference and improvement in appearance of abdomen in postpartum women, without compromising patients' safety.

Forensic dental identification using two-dimensional photographs of a smile and three-dimensional dental models: A 2D-3D superimposition method

Photographs of a person smiling may provide valuable information about their anterior dentition. These images can be an alternative ante-mortem (AM) dental source in cases with no dental records, which gives the forensic odontologist a significant opportunity for comparative dental analysis. There are no reported studies that have investigated the reliability of a superimposition technique using 2D photographs of a smile and 3D dental models in dental identification. The aim of this study was to explore novel odontological methods by combining 2D photographs with 3D dental models, simulating a dental identification scenario. The objective was to increase the accuracy of dental identification using an AM photograph with the aid of 3D imaging as an alternative to post-mortem (PM) photographs. The study comprised of 31 3D dental models (simulating PM information) and 35 digital photographs (simulating AM information). The data was analysed in two phases: Phase I- Visual Comparison of 2D-3D images and Phase II- 2D-3D superimposition after a wash out period. Both methods were analysed by the principal investigator. Further, one-third (ten) of the sample was evaluated by six raters (three experienced forensic odontologists and three forensic odontology MSc. students). The inter-rater agreement was assessed using intra-class correlation (ICC 2, 1, absolute). The results of the study suggest that the inter-rater and intra-rater reliability using 3D superimposition was highest (ICC ≈ 1.0). In summary, there was an increase in match rates and higher certainty among the opinions reached when using the 2D-3D superimposition method. The procedure attempted to reduce the limitations of previously existing 2D methods and is intended to assist forensic experts with an alternative method in dental identification when expressing conclusions on a case using photographs.

Assessing Facial Asymmetry in Postoperative Patients With Unilateral Coronal Craniosynostosis.

Despite surgical correction of unilateral craniosynostosis (ULC), complex cranial base angulation can result in partial reversion to preoperative deformity with growth and time. Using 3-dimensional imaging, dysmorphic facial features of ULC in school-age patients were quantified and related to how they contribute to overall facial asymmetry and patient-reported outcomes. Children who underwent surgical correction of ULC were recruited from Yale University and Children's Hospital of Philadelphia. The 3D photographs were analyzed utilizing a Procrustes analysis of shape. Pearson's correlation was used to determine dysmorphic features' impact on overall asymmetry. Patients were stratified into "moderate" and "severe" asymmetry. Finally, asymmetry was correlated to patient-reported outcome scores. Statistical analysis was performed with SPSS-25 with P < 0.05 as statistically significant. Twenty-one patients were included with average age at analysis of 12.3 years. Fifty-seven percent of patients had right-sided fusion. The overall Procrustes analysis indicated a root mean square difference of 2.21 mm. Pearson's correlation indicated that the facial middle 3rd (P ≤ 0.001), orbital dystopia (P < 0.001), chin point deviation (P = 0.011), and nasal root angulation (P = 0.019) contributed most to overall asymmetry. Patients in the severe asymmetry cohort had greater facial middle-third asymmetry (P < 0.001) and orbital dystopia (P < 0.001). Asymmetry did not correlate with patient-reported outcomes. Patients with ULC have persistent facial asymmetry at school-age with the greatest levels of asymmetry in the facial middle-third, orbit, and nasal root. Beyond the cranial dysmorphology, initial skull base angulation in unilateral coronal craniosynostosis manifests in long-term mid and lower-third facial asymmetry.

Quantitative evaluation of rejuvenation treatment of nasolabial fold wrinkles by regression model and 3D photography.

With the application of 3D photography, our study aimed to quantify parameters of static nasolabial fold wrinkles and establish mathematic regression model between parameters of wrinkles and age, further to quantitatively evaluate the effect of rejuvenation treatment in terms of age. From October 2016 to May 2018, 433 Chinese female volunteers, aged 25-60years old, were enrolled in this study. Antera 3D camera was used to collect four parameters of static nasolabial fold wrinkles on the left and right sides of the volunteers, including overall size, average depth (mm), average width (mm), and maximum depth (mm). For those presented a linear relationship with age, univariate linear regression fitting was performed, followed by residual analysis, goodness of fit test, and significance test. The results of univariate linear regression fitting showed there was a clear linear relationship between the maximum depth, average depth, overall size of nasolabial fold wrinkles and age, and the regression equations were established. The significance test of regression coefficients showed P values were less than .0001. With application of the regression model between parameters of nasolabial fold wrinkles and age, the effect of rejuvenation treatment can be quantitatively evaluated in terms of age, which has certain reference and promotion value.

Pitfalls and Promise of 3-dimensional Image Comparison for Craniofacial Surgical Assessment.

Summary:Three-dimensional (3D) photography is becoming widely used in plastic surgery. It provides an accurate and reproducible record of the facial surface anatomy and could be a versatile tool for treatment planning and assessment. However, the existing software tools available for the assessment of 3D facial imaging often give highly misleading results. The goal of this special topic article is to give clinicians an insight into methods of 3D image assessment and explain the reasons why results may be misleading. We point toward the advantages of an alternative approach using “nonrigid surface registration” for the comparison of pre- and postsurgical images. This approach is compared with the regular rigid surface registration, and this is illustrated by the assessment of a child with Crouzon syndrome before and after LeFort III osteotomy and distraction. Findings of the standard method imply that changes have occurred that are anatomically not possible, whereas the alternative approach indicates realistic changes. Furthermore, we demonstrate an exciting capacity of 3D image analysis to construct reference populations of normal head size and shape. These can be used to assess the parts of the head that are normal and abnormal pre- and posttreatment of the same child. We conclude that, while 3D image analysis has great potential in surgical assessment, existing software does not always give an adequate assessment. Collaboration among surgeons and engineering and computer science specialists should be encouraged. This way, more comprehensive and accurate techniques in patient assessment and surgical planning can be developed and applied in clinical practice.

Viewing garden scenes: Interaction between Gaze Behavior and Physiological Responses.

Previous research has shown that exposure to Japanese gardens reduces physiological measures of stress, e.g. heart rate, in both healthy subjects and dementia patients. However, the correlation between subjects’ physiological responses and their visual behavior while viewing the garden has not yet been investigated. To address this, we developed a system to collect simultaneous measurements of eye gaze and three physiological indicators of autonomic nervous system activity: electrocardiogram, blood volume pulse, and galvanic skin response. We recorded healthy subjects’ physiological/behavioral responses when they viewed two environments (an empty courtyard and a Japanese garden) in two ways (directly or as a projected 2D photograph). Similar to past work, we found that differences in subject’s physiological responses to the two environments when viewed directly, but not as a photograph. We also found differences in their behavioral responses. We quantified subject’s behavioral responses using several gaze metrics commonly considered to be measures of engagement of focus: average fixation duration, saccade amplitude, spatial entropy and gaze transition entropy. We found decrease in gaze transition entropy, the only metric that accounts for both the spatial and temporal properties of gaze, to have a weak positive correlation with decrease in heart rate. This suggests a relationship between engagement/focus and relaxation. Finally, we found gender differences: females’ gaze patterns were more spatially distributed and had higher transition entropy than males.

Evaluation of Ground Plane Detection for Estimating Breast Height in Stereo Images

Abstract Diameter at breast height is a standard method for characterizing trees and ultimately forests over large geographical scales. Expressing the cross-section of a tree stem with a diameter measurement has inherent errors, as stems are not perfect conical frustums. Diameter suffices as an approximation, since methods for the exact cross-sectional area of a stem are infeasible in practice. There are other primary sources of error in diameter at breast height measurements: diameter measurement error and breast height measurement error. This paper addresses the latter in the context of an automated measurement system using 3D photography. We consider breast height estimation a fundamental component in such systems, as errors in measurement height can precipitate significant errors in stand-level attribute estimation as diameter changes along the height of the stem because of taper. We evaluate the efficacy of breast height estimation using stereo photogrammetry by fitting a planar surface to the ground and elevating the plane to breast height. Results from a validation test on 560 observations show that breast height can be estimated with a root mean squared error of 10.20 cm within 10 m from the camera and 13.36 cm within 20 m from the camera on flat terrain in varying levels of stem density. Study Implications Increasing the level of automation in forest operations is one approach to address workforce attrition and safety issues in the industry. Automated tree measurement and mapping systems present an opportunity to reduce operational costs by providing machine operators with necessary information to carry out silvicultural prescriptions and eliminate the need for individual tree marking in certain situations. In order to maintain trust between landowners and harvesting contractors, it is imperative that automatic measurement systems are rigorously tested to determine that measurement accuracy is within acceptable limits. Breast height measurement error is often overlooked as a source of error in estimating diameter at breast height. However, accurate breast height estimation is a necessary prerequisite for reliable, consistent, and precise diameter at breast height measurement. The capacity of machine vision systems to automate forest inventory and monitoring tasks is increasing and can help managers achieve sustainable forestry objectives on more acres in less time.

3D light-field endoscopic imaging using a GRIN lens array

Endoscopic observation of biological tissues with quantitative depth perception, effective volumetric recognition of anatomical features, and efficient 3D navigation is critical for optical diagnostics and minimally invasive surgery for various target diseases. Light-field techniques have recently emerged as a promising approach to 3D photography and microscopy due to their scanning-free, highly scalable, and volumetric imaging capabilities. These advantages hold great potential for application to optical endoscopy, as the existing clinical endoscopy systems rely primarily on a 2D projection or use polarized glasses to provide visual parallax of complex 3D structures. Here, we report a light-field endoscopy prototype using a GRIN lens array (GLA). The GLA-based system maintains consistent spatial measurements with clinical endoscopic systems, a compact size in comparison with compound objective lenses, as well as the ability to maximally capture the angular information necessary for 3D imaging. We also present a computational strategy combining a wave-optics model and a hybrid point-spread function for high-resolution volumetric reconstruction. The system achieves spatial resolutions of 20–60 μm and 100–200 μm in the lateral and axial dimensions, respectively, across an imaging volume of ∼5 mm × 5 mm × 10 mm. We anticipate the prototype to offer a promising paradigm for glasses-free, high-resolution 3D medical endoscopy.