Optical 3D Research Articles

Autonomous flight strategy of an unmanned aerial vehicle with multimodal information for autonomous inspection of overhead transmission facilities

AbstractThis study proposes an innovative method for achieving autonomous flight to inspect overhead transmission facilities. The proposed method not only integrates multimodal information from novel sensors but also addresses three essential aspects to overcome the existing limitations in autonomous flights of an unmanned aerial vehicle (UAV). First, a novel deep neural network architecture titled the rotational bounding box with a multi‐level feature pyramid transformer is introduced for accurate object detection. Second, a safe autonomous method for the transmission tower approach is proposed by using multimodal information from an optical camera and 3D light detection and ranging. Third, a simple yet accurate control strategy is proposed for tracking transmission lines without necessitating gimbal control because it keeps the UAV's altitude in sync with that of the transmission lines. Systematic analyses conducted in both virtual and real‐world environments confirm the effectiveness of the proposed method. The proposed method not only enhances the performance of autonomous flight but also provides a safe operating platform for inspection personnel.

Сonceptual Foundations оf Applying Innovative 3d Scanning Technologies іn the Context of Maintaining Airworthiness of State Aviation Equipment

The goal of this article is to analyze the use of modern 3D scanning technologies and additivemanufacturing in addressing practical needs to maintain airworthiness of state aviation equipment. The unified algorithm for 3D scanning of complex technical objects which is independent of specific methods and equipment types has been developed as well as the detailed description of each step of the algorithm. Innovative optical methods of 3D scanning technologies are explored, and a comprehensive methodology that utilizes these optical 3D scanning methods for determining the potential improvement of identified resource indicators of aviation equipment is proposed.

Low-cost 3D printed lenses for brightfield and fluorescence microscopy.

We present the fabrication and implementation of low-cost optical quality 3D printed lenses, and their application as microscope objectives with different prescriptions. The imaging performance of the 3D printed lenses was benchmarked against commercially available optics including a 20 mm focal length 12.7 mm diameter NBK-7 plano-convex lens used as a low magnification objective, and a separate high magnification objective featuring three 6 mm diameter NBK-7 lenses with different positive and negative focal lengths. We describe the design and manufacturing processes to produce high-quality 3D printed lenses. We tested their surface quality using a stylus profilometer, showing that they conform to that of commercial glass counterpart lenses. The 3D printed lenses were used as microscope objectives in both brightfield and epi-fluorescence imaging of specimens including onion, cyanobacteria, and variegated Hosta leaves, demonstrating a sub-cellular resolution performance obtained with low-cost 3D printed optical elements within brightfield and fluorescence microscopy.

Extrinsic Calibration for a Modular 3D Scanning Quality Validation Platform with a 3D Checkerboard.

Optical 3D scanning applications are increasingly used in various medical fields. Setups involving multiple adjustable systems require repeated extrinsic calibration between patients. Existing calibration solutions are either not applicable to the medical field or require a time-consuming process with multiple captures and target poses. Here, we present an application with a 3D checkerboard (3Dcb) for extrinsic calibration with a single capture. The 3Dcb application can register captures with a reference to validate measurement quality. Furthermore, it can register captures from camera pairs for point-cloud stitching of static and dynamic scenes. Registering static captures from TIDA-00254 to its reference from a Photoneo MotionCam-3D resulted in an error (root mean square error ± standard deviation) of 0.02 mm ± 2.9 mm. Registering a pair of Photoneo MotionCam-3D cameras for dynamic captures resulted in an error of 2.2 mm ± 1.4 mm. These results show that our 3Dcb implementation provides registration for static and dynamic captures that is sufficiently accurate for clinical use. The implementation is also robust and can be used with cameras with comparatively low accuracy. In addition, we provide an extended overview of extrinsic calibration approaches and the application's code for completeness and service to fellow researchers.

Surface Degradation of Ion-releasing Restorative Materials With Cariogenic Challenge.

This study examined the influence of cariogenic environments on the surface roughness of ion-releasing restorative materials (IRMs). Custom-made stainless steel molds with holes of 5 mm × 2mm were used to fabricate 60 disc-shaped specimens of each of the following materials: Activa Bioactive (AV), Beautifil Bulk Restorative (BB), Cention N (Bulk-fill) (CN), and Filtek Z350XT (FZ) (Control). Baseline surface roughness (Ra) measurements were obtained using an optical 3D measurement machine (Alicona Imaging GmbH, Graz, Austria). The specimens were then randomly divided into five subgroups (n=12) and exposed to 10 ml of the following mediums at 37°C: distilled water (DW), demineralization solution (DM), remineralization solution (RM), pH cycling (PC) and air (AR) (control). Ra measurements were again recorded after one week and one month, followed by statistical evaluations with two-way analysis of variance (ANOVA) to determine interactions between materials and mediums. One-way ANOVA and post hoc Games Howell tests were performed for intergroup comparisons at a significance level of 0.05. Mean Ra values ranged from 0.085 ± 0.004 (µm) to 0.198 ± 0.001 µm for the various material-medium combinations. All IRMs showed significant differences in Ra values after exposure to the aqueous mediums. The smoothest surfaces were observed in the AR for all materials. When comparing materials, AV presented the roughest surfaces for all mediums. All IRM materials showed increased surface roughness over time in all cariogenic environments but were below the threshold value for bacterial adhesion, except for AV 1-month post immersion with pH cycling. Therefore, besides AV, the surface roughness of IRMs did not deteriorate to an extent that it is clinically relevant.

The Automatic Algorithm of Optimizing the Position of Structured Light Sensors

Optical 3D detection technology has a wide range of applications in industrial detection, agricultural production, and so on. Its advantages are non-contact, efficiency, and high precision. However, the specular reflection problem affects model coverage and measurement accuracy. An optimization algorithm for calculating the number and pose of sensors has been proposed to address this issue. First, the specular reflection problem is viewed as a multi-sensor position search problem. Then, an optimization algorithm is used to find the optimal number and bit positions of sensors to avoid specular reflection. The experiment shows that the optimization results of this algorithm can cover the area to be measured with the least number of sensor combinations while avoiding the influence of specular reflection.

Sonar Image Target Detection Based on Simulated Stain-like Noise and Shadow Enhancement in Optical Images under Zero-Shot Learning

There are many challenges in using side-scan sonar (SSS) images to detect objects. The challenge of object detection and recognition in sonar data is greater than in optical images due to the sparsity of detectable targets. The complexity of real-world underwater scanning presents additional difficulties, as different angles produce sonar images of varying characteristics. This heterogeneity makes it difficult for algorithms to accurately identify and detect sonar objects. To solve these problems, this paper presents a novel method for sonar image target detection based on a transformer and YOLOv7. Thus, two data augmentation techniques are introduced to improve the performance of the detection system. The first technique applies stain-like noise to the training optical image data to simulate the real sonar image environment. The second technique adds multiple shadows to the optical image and 3D data targets to represent the direction of the target in the sonar image. The proposed method is evaluated on a public sonar image dataset, and the experimental results demonstrate that the proposed method outperforms the state-of-the-art methods in terms of accuracy and speed. The experimental results show that our method achieves better precision.

Direct fringe projection profilometry based on the spatial frequency distribution function in optical 3D imaging

Phase unwrapping has been a big hurdle in conventional optical three-dimensional (3D) measurement technologies, badly affecting speed and accuracy. To skip the complicated step of phase unwrapping, a direct fringe projection profilometry based on the spatial frequency distribution function is presented in this paper. First, the spatial frequency distribution function is defined according to the physical meaning of spatial frequency. Then, direct phase-shift method and direct Fourier transform profilometry are developed respectively with reference to the conventional fringe projection profilometry. Finally, both numerical simulations and experiments were carried out to test the proposed direct fringe projection profilometry. The direct phase-shift method without phase unwrapping combines the advantages of the conventional in terms of high accuracy, while the direct Fourier transform method does not get rid of the drawbacks of the conventional in spectral aliasing although it skips the phase unwrapping procedure.

The features of dome-shape Macula and related complications in high myopia on optical coherence tomography.

This study used optical coherence tomography scanning and 3D reconstruction of the macular region in high myopia to examine more thoroughly and carefully the differences between high myopia-related macular complications with and without dome-shape macula (DSM) and to determine whether the DSM's fine structure has an effect on them. Retrospective analysis of the medical records of 345 eyes with high myopia who underwent an optical coherence tomography (OCT) examination. They were divided into the DSM group (69 eyes) and the group without DSM (276 eyes). Macular complications between the two groups were compared. The height of the DSM and the diameter of the dome base were measured. And then the association between DSM type, protrusion height and macular problems were analyzed. Epiretinal membrane (ERM) and extrafoveal schisis occurred more frequently in the DSM group, but the was no statistically significant difference in the frequency of foveal schisis between the two groups. The majority of eyes in the DSM categorization had a horizontal oval-shaped domain. In the DSM group, there was no evident difference in the percentage of eyes with macular complications in the groups below 150 um and above 150 um. OCT examination-based fine macular structure analysis reveals that DSM affects various macular problems in distinct ways. DSM could increase the risk of extrafoveal schisis and ERM while decreasing the risk of foveal schisis. The height of the DSM had no obvious impact on the prevalence of macular complications.

Diamond-like carbon coating reduces connection screw head stripping after multiple tightening.

The stability of implant-abutment joint is fundamental for the long-term success of implant rehabilitation. The screw loosening, fracture, and head deformation are among the most common mechanical complications. Several surface treatments of titanium screws have been proposed to improve their resistance and stability. Diamond-like carbon (DLC) coating of the materials is widely used to increase their wear resistance and durability. The present study aimed to evaluate the effect of carbon fiber coating on the screw head on screw removal torque and screw head stripping. One hundred titanium implant screws were used, 50 without coating (Group 1) and 50 with DLC coating of the screw head (Group 2). Each screw was tightened with a torque of 25Ncm and unscrewed ten times. The removal torque was measured with a digital cap torque tester for each loosening. Optical 3d measurement of the screw head surface was performed by a fully automatic machine before and after multiple tightening to investigate surface modifications. The reverse torque values decreased with repeated tightening and loosening cycles in both groups without significant differences (p>0.05). Optical measurements of surface dimensions revealed average changes of 0.0357mm in Group 1 and 0.02312mm in Group 2, which resulted to be statistically significant (p<0.001). The DLC coating of the retention screw head can prevent its distortion and wear, especially after multiple tightening.

Comparison of optical 3D scanner and coordinate measurement system from the standpoint of macro-geometry measurement

The aim of the experiment described in the paper was to determine the possibility of using an optical 3D scanner to measure the macro-geometry of cutting tools. To verify this possibility, a precise component was measured, and the accuracy of optical 3D scanner was compared to a tactile coordinate measurement machine. A precise cemented carbide rod was used as a reference part and the measurement data were compared with the measurement result from the ZEISS Prismo coordinate measurement machine. The data obtained from the measurements were evaluated and compared. The experiment was carried out so that the use of an optical 3D scanner to measure cutting tools could be verified based on the desired requirements. Both dimensions and geometrical tolerancing – circularity were measured. The experiment has shown that an optical 3D scanner can achieve sufficient accuracy for the purpose of measuring macro-geometry of cutting tools.

Dual-mode optical see-through integral imaging 3D display with large depth of field

Conventional optical see-through integral imaging display system using holographic optical element (HOE) is actually in focused display mode whose central depth plane (CDP) is very close to the HOE plane, and the depth of field (DOF) of the system is limited to several centimeters around the HOE plane. In this paper, we proposed a dual-mode optical see-through integral imaging display system to reconstruct 3D images in both real and virtual display modes simultaneously and greatly extend the DOF. A dual-mode lens array HOE (DM-LAHOE) was specially designed by using two sets of lens arrays, and it featured as a lens array with positive focal length and negative focal length under the illumination of different probe beams. The designed DM-LAHOE can generate two CDPs away from the HOE plane. Hence, the real mode and virtual mode of the integral imaging display can be achieved simultaneously, and the DOF of the system was greatly improved by increasing the focal length of the recorded lens array and the number of CDPs. In the experiment, the DM-LAHOE with large focal lengths of ±14mm was fabricated, and the DOF of the proposed system was increased from 24.5mm to 190mm. The proposed dual-mode optical see-through integral imaging display system is expected to be applied in the fields of augmented reality display, vehicle display, window display, etc.

Vision-Based Optical 3D Reconstruction and the Application in Crop Information Perception

Vision-Based Optical 3D Reconstruction and the Application in Crop Information Perception

Research on carbon deposition method and characterization of nozzle in direct injection gasoline engine

Based on Geely JLE-4G18TDB 1.8T gasoline engine stand and optical 3D profile measuring instrument, this paper explores the rapid carbon accumulation process and characterization about carbon deposition of nozzle in a direct injection gasoline engines. By using aging accelerators, cycle conditions and long-term fuel pulse width correction coefficient, rapid carbon accumulation close to actual road conditions is achieved. The carbon accumulation situation of the nozzle was mastered in the state of the engine without stopping, and the carbon accumulation characteristics of the nozzle were characterized by optical means. The volume data, three-dimensional image and carbon volume distribution map of the injector before and after carbon deposition were obtained under the condition that the carbon in the surface area of the injector was not destroyed, which played an important role in the evaluation of the gasoline purifier and purifier synergist.

Optical Sensor-Based Image Texture Characterization for Image Simulation Applications in College Gymnastics Instruction

Abstract Gymnastics learning is characterized by imitation and reference, and a teaching model combining optical sensors and image simulation systems may have promising results in college gymnastics courses. Based on the introduction of the meaning of college gymnastics teaching, the article sorted out the value performance of the image teaching mode and also established an optical three-dimensional imaging system based on optical sensors for gymnastics movement to obtain gymnastic images. In the optical 3D imaging system, the acquisition error of gymnastics images is reduced by using the finite distance image measurement method, and the quality of gymnastics images is enhanced by adaptive bilateral filtering and adaptive threshold selection of the Canny operator by the OTSU method. The enhanced gymnastics images are then inputted into a panoramic graphic imaging simulation system, and a gymnastics image simulation teaching model is established for colleges and universities. The effectiveness of the gymnastics image simulation teaching model is analyzed through a teaching comparison test conducted during simulation verification for optical imaging. In the optical imaging system, when the measurement distance is about 150m, the measurement error range is between [15″and 30″], and the MSE value of the gymnastic enhanced image obtained by the improved Canny algorithm decreases by 46.97% compared with the MSE value before the improvement. The students’ handstand score against the wall improved by 22.63 points compared to before the experiment, and more than 90% of the students were satisfied with the gymnastics image simulation teaching method. The teaching mode is constructed with the optical sensor to obtain the image characteristics of gymnastics movement, and the simulation system is innovative, which effectively promotes students’ interest in learning gymnastics courses and enhances their gymnastics training level.

Bond strength measurement of composite materials using an optical 3D printer (LCD type)

Bond strength measurement of composite materials using an optical 3D printer (LCD type)

High-speed optical 3D measurement device for quality control of aircraft rivet

High-speed optical 3D measurement device for quality control of aircraft rivet

RESEARCH ON 3D MEASUREMENT TECHNOLOGY BASED ON MACHINE VISION

Measurement is an important means for humans to understand and transform the world, and it is the technological foundation for breaking through the forefront of science and solving major problems in economic and social development. The three-dimensional measurement system serves primary national needs, leads national economic development, and ensures national defense security. With the arrival of a new industrial revolution, major industrial countries worldwide have begun to accelerate the strategic deployment of intelligent manufacturing. As an essential component of the construction of smart factories and lighthouse factories, the 3D measurement system will play a vital role in deepening the implementation of the manufacturing power strategy and promoting the high-end, intelligent, and green manufacturing process. In recent years, optical 3D measurement technology represented by surface structured light has developed rapidly and has been widely applied in multiple material processing fields such as forging, casting, and sheet metal. To analyze the manufacturing accuracy of complex parts using surface structured light 3D measurement technology, it is necessary to first scan and reconstruct the overall 3D surface of the part. The reconstructed 3D point cloud data of the part surface should be roughly and precisely matched with the design model. Finally, based on this, data comparison and accuracy analysis should be carried out according to the actual detection requirements of different types of parts. In this process, the accuracy of 3D reconstruction of complex parts and the alignment accuracy between the reconstruction results and the design model directly determine the reliability and accuracy of the final part manufacturing and machining accuracy analysis. This article uses cases to illustrate the application of machine vision in 3D online measurement. The application of three-dimensional measurement technology in online quality inspection and grinding of blades can not only improve the measurement accuracy of online quality inspection of blades but also maintain the relative stability of robot grinding force and improve the grinding effect in robot grinding of aircraft engine blades. Applied to online quality inspection of train wheel hubs, three-dimensional measurement of train wheel adapters and high-speed train wheel size online inspection has been achieved.

Tribological Investigation of Glass Fiber Reinforced Polymer Composites against 52100 Chrome Alloy Steel Based on ELECTRE Decision-Making Method.

Fibers play an important role when studying the tribological behavior of reinforced friction composites. The purpose of the current research is to develop a glass fiber reinforced polymer (GFRP) recipe with improved tribological properties as well as to find the composites with the optimal tribological behavior. A ball-on-disc tribometer was used to perform dry sliding friction testing, the obtained results were then analyzed with the ELECTRE (ELimination Et Choix Traduisant la REalite-elimination and choice translating the reality) method based on a utility matrix having process parameters the applied load, sliding velocity, and weight percentage of the fiber content. The ELECTRE method was chosen to find the optimal tribological parameters, with respect to more performance criteria, because it is one of the best multiple criteria decision-making methods. The optimal combination of parameters for the multi-response characteristics of the investigated friction composite was at an applied load of 10 N, a sliding velocity of 0.1 ms-1 and a 54% weight fiber content. The results showed that the addition of glass fiber (GF) content did not considerably improve the tribological behavior of the friction composites. In addition, from the nano focus-optical 3D scanning electron microscopy, images of the friction, tested friction and wear composites, plate formation, fiber-matrix delamination, fiber pull-out, and matrix cracking and damage, various wear mechanisms were identified.

Dual-stage hybrid network for single-shot fringe projection profilometry based on a phase-height model.

Single-shot fringe projection profilometry (FPP) is widely used in the field of dynamic optical 3D reconstruction because of its high accuracy and efficiency. However, the traditional single-shot FPP methods are not satisfactory in reconstructing complex scenes with noise and discontinuous objects. Therefore, this paper proposes a Deformable Convolution-Based HINet with Attention Connection (DCAHINet), which is a dual-stage hybrid network with a deformation extraction stage and depth mapping stage. Specifically, the deformable convolution module and attention gate are introduced into DCAHINet respectively to enhance the ability of feature extraction and fusion. In addition, to solve the long-standing problem of the insufficient generalization ability of deep learning-based single-shot FPP methods on different hardware devices, DCAHINet outputs phase difference, which can be converted into 3D shapes by simple multiplication operations, rather than directly outputting 3D shapes. To the best of the author's knowledge, DCAHINet is the first network that can be applied to different hardware devices. Experiments on virtual and real datasets show that the proposed method is superior to other deep learning or traditional methods and can be used in practical application scenarios.