Evaluation of permissible pixel positioning errors for displaying computer-generated holograms in projection photolithography

Objectives: To assess dental students’ ability to recognize head positioning errors in panoramic (PAN) images after individual learning via computer-assisted-learning (CAL) and in a simulation clinic (SIM). Both cognitive skills and performance in patient examination were assessed. Methods and materials: 60 students (mean age 23.25 years) participated in lectures on the relation between PAN-image errors and patient’s head position. Immediately after they took a test, based on which they were randomized to three groups: control (CON) group, CAL group, and SIM group (both CAL and training in a simulation clinic with a phantom). 4–5 weeks after intervention/no intervention, all students individually examined a patient with PAN-exposure. A blinded rater, not knowing group allocation, supervised patient exposure and assessed student’s performance (correct/incorrect head position in three planes). 1–2 weeks after, the students scored positioning errors in 40 PAN-images. Differences in cognitive test scores between groups were evaluated by ANOVA and in patient examination by χ2 tests, and within-group differences by sign-tests. Results: No statistically significant difference in cognitive test scores was seen between the SIM and CAL group, while the CON group scored lower (p < 0.003). In all groups, several students positioned the patient incorrectly in the Frankfort horizontal plane. All students performed well in the sagittal plane. Students in SIM group positioned the patient more correctly in the coronal plane. Conclusions: Training with CAL increased students’ cognitive skills compared with a control group. Simulated patient exposure with a phantom increased to some extent their performance skills in examination of patients.

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High-Precision RTT-Based Indoor Positioning System Using RCDN and RPN

Sensors ◽

10.3390/s21113701 ◽

2021 ◽

Vol 21 (11) ◽

pp. 3701

Author(s):

Ju-Hyeon Seong ◽

Soo-Hwan Lee ◽

Won-Yeol Kim ◽

Dong-Hoan Seo

Keyword(s):

High Precision ◽

Distance Estimation ◽

Sampling Period ◽

Multipath Fading ◽

Indoor Positioning ◽

Positioning System ◽

Positioning Systems ◽

Positioning Errors ◽

Location Determination ◽

Indoor Positioning System

Wi-Fi round-trip timing (RTT) was applied to indoor positioning systems based on distance estimation. RTT has a higher reception instability than the received signal strength indicator (RSSI)-based fingerprint in non-line-of-sight (NLOS) environments with many obstacles, resulting in large positioning errors due to multipath fading. To solve these problems, in this paper, we propose high-precision RTT-based indoor positioning system using an RTT compensation distance network (RCDN) and a region proposal network (RPN). The proposed method consists of a CNN-based RCDN for improving the prediction accuracy and learning rate of the received distances and a recurrent neural network-based RPN for real-time positioning, implemented in an end-to-end manner. The proposed RCDN collects and corrects a stable and reliable distance prediction value from each RTT transmitter by applying a scanning step to increase the reception rate of the TOF-based RTT with unstable reception. In addition, the user location is derived using the fingerprint-based location determination method through the RPN in which division processing is applied to the distances of the RTT corrected in the RCDN using the characteristics of the fast-sampling period.

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Occlusion Culling for Wide-Angle Computer-Generated Holograms Using Phase Added Stereogram Technique

Photonics ◽

10.3390/photonics8080298 ◽

2021 ◽

Vol 8 (8) ◽

pp. 298

Author(s):

Juan Martinez-Carranza ◽

Tomasz Kozacki ◽

Rafał Kukołowicz ◽

Maksymilian Chlipala ◽

Moncy Sajeev Idicula

Keyword(s):

Point Sources ◽

Wide Angle ◽

Computer Generated Holograms ◽

Propagation Methods ◽

Propagation Technique ◽

3D Scene ◽

Occlusion Culling ◽

Fourier Type ◽

Cloud Of Points

A computer-generated hologram (CGH) allows synthetizing view of 3D scene of real or virtual objects. Additionally, CGH with wide-angle view offers the possibility of having a 3D experience for large objects. An important feature to consider in the calculation of CGHs is occlusion between surfaces because it provides correct perception of encoded 3D scenes. Although there is a vast family of occlusion culling algorithms, none of these, at the best of our knowledge, consider occlusion when calculating CGHs with wide-angle view. For that reason, in this work we propose an occlusion culling algorithm for wide-angle CGHs that uses the Fourier-type phase added stereogram (PAS). It is shown that segmentation properties of the PAS can be used for setting efficient conditions for occlusion culling of hidden areas. The method is efficient because it enables processing of dense cloud of points. The investigated case has 24 million of point sources. Moreover, quality of the occluded wide-angle CGHs is tested by two propagation methods. The first propagation technique quantifies quality of point reproduction of calculated CGH, while the second method enables the quality assessment of the occlusion culling operation over an object of complex shape. Finally, the applicability of proposed occlusion PAS algorithm is tested by synthetizing wide-angle CGHs that are numerically and optically reconstructed.

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A non-overshooting controller for vehicle path following

Transactions of the Institute of Measurement and Control ◽

10.1177/0142331221994384 ◽

2021 ◽

pp. 014233122199438

Author(s):

Tong Xu ◽

Dong Wang ◽

Weigong Zhang

Keyword(s):

Field Experiments ◽

Fitness Function ◽

Path Following ◽

Settling Time ◽

Distribution Model ◽

Positioning Errors ◽

Guidance Law ◽

Initial Control ◽

Vehicle Path ◽

Pavement Construction

Unmanned pavement construction is of great significance in China, and one of the most important issues is how to follow the designed path near the boundary of the pavement construction area to avoid curbs or railings. In this paper, we raise a simple yet effective controller, named the proportional-integral-radius and improved particle swarm optimization (PIR-IPSO) controller, for fast non-overshooting path-following control of an unmanned articulated vehicle (UAV). Firstly, UAV kinematics model is introduced and segmented UAV steering dynamics model is built through field experiments; then, the raw data collected by differential global positioning system (DGPS) is used to build the measurement error distribution model that simulates positioning errors. Next, line of sight (LOS) guidance law is introduced and the LOS initial parameter is assigned based on human driving behavior. Besides, the initial control parameters tuned by the Ziegler-Nichols (ZN) method are used as the initial iterative parameters of the PSO controller. An improved PSO fitness function is also designed to achieve fast non-overshoot control performance. Experiments show that compared with the PSO, ZN and ZN-PSO controller, the PIR-PSO-based controller has significantly less settling time and almost no overshoot in various UAV initial states. Furthermore, compared with other controllers, the proposed PIR-IPSO-based controller achieves precise non-overshoot control, relatively less settling time and centimeter-level positioning error in various initial deviations.

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Computer-Generated Hologram Based on Reference Light Multiplexing for Holographic Display

Applied Sciences ◽

10.3390/app11167199 ◽

2021 ◽

Vol 11 (16) ◽

pp. 7199

Author(s):

Dapu Pi ◽

Juan Liu

Keyword(s):

Image Quality ◽

Numerical Simulations ◽

Light Wave ◽

Information Capacity ◽

Improve Image Quality ◽

Multiple Images ◽

Holographic Display ◽

Light Waves ◽

Computer Generated Holograms ◽

Holographic Displays

In this article, we propose a reference light wave multiplexing scheme to increase the information capacity of computer-generated holograms. The holograms were generated by different reference light waves and superimposed together as a multiplexed hologram. A modified Gerchberg–Saxton algorithm was used to improve image quality, and different images could be reconstructed when the multiplexed hologram was illuminated by corresponding reference light waves. We performed both numerical simulations and optical experiments to demonstrate the feasibility of the proposed scheme. Numerical simulations showed that the proposed method could reconstruct multiple images successfully by a single multiplexed hologram and optical experiments are consistently good with numerical simulations. It is expected that the proposed method has great potential to be widely applied in holographic displays in the future.

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NLOS Multipath Classification of GNSS Signal Correlation Output Using Machine Learning

Sensors ◽

10.3390/s21072503 ◽

2021 ◽

Vol 21 (7) ◽

pp. 2503

Author(s):

Taro Suzuki ◽

Yoshiharu Amano

Keyword(s):

Machine Learning ◽

Satellite System ◽

Training Data ◽

Support Vector ◽

Positioning Errors ◽

Automated Method ◽

Global Navigation Satellite ◽

Better Than ◽

Signal Correlation

This paper proposes a method for detecting non-line-of-sight (NLOS) multipath, which causes large positioning errors in a global navigation satellite system (GNSS). We use GNSS signal correlation output, which is the most primitive GNSS signal processing output, to detect NLOS multipath based on machine learning. The shape of the multi-correlator outputs is distorted due to the NLOS multipath. The features of the shape of the multi-correlator are used to discriminate the NLOS multipath. We implement two supervised learning methods, a support vector machine (SVM) and a neural network (NN), and compare their performance. In addition, we also propose an automated method of collecting training data for LOS and NLOS signals of machine learning. The evaluation of the proposed NLOS detection method in an urban environment confirmed that NN was better than SVM, and 97.7% of NLOS signals were correctly discriminated.

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Design and Fabrication of Computer Generated Holograms for Fresnel Domain Lithography

Advances in Imaging ◽

10.1364/dh.2009.dwb3 ◽

2009 ◽

Author(s):

José A. Domínguez-Caballero ◽

Satoshi Takahashi ◽

Sung Jin (James) Lee ◽

George Barbastathis

Keyword(s):

Computer Generated Holograms

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