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Retro filament white light-emitting diodes (WLEDs) have attracted great attention and are widely welcomed by consumers. The results of an investigation for the optical and thermal performance of filament-like WLEDs with various packaging structures are presented in detail. The optical simulation shows that the phosphor concentration on the chip-bonding side makes a great contribution to increasing backscattered blue light power. It means the backside should be packaged to improve blue light utilization. By controlling the phosphor coating structure, several filament-like LEDs were fabricated and subsequently investigated. The luminous efficacy (LE), correlated color temperature (CCT) and thermal reliability were measured, and then the structures were proposed and optimized. The optimal structure can maintain the equivalent LE compared with others under almost the same CCT. The CCT and light intensity spatial distribution were also analyzed based on the phosphor structure. The phosphor on the chip-bonding side contributes significantly to the CCT deviation. Consequently, the proposed structure filament-like WLEDs exhibited 2.23 and 5.42 ° lower working temperatures than the half packaging and full packaging structures under a driving current of 15 mA, respectively. Besides, the no-middle packaging structure was investigated in detail for optimal optical performance. After optimization, when the back surface dispensed $20~\mu \text{L}$ of phosphor resin, the LE increased from 182.9 to 188.3 lm/W at similar CCT with the CCT deviation changed from 1062 to 154.5 K significantly. Therefore, it was revealed that optimizing the packaging structure is an efficient method of enhancing the performance of filament-like WLEDs.

Recently, RGBD-based category-level 6D object pose estimation has achieved promising improvement in performance, however, the requirement of depth information prohibits broader applications. In order to relieve this problem, this paper proposes a novel approach named Object Level Depth reconstruction Network (OLD-Net) taking only RGB images as input for category-level 6D object pose estimation. We propose to directly predict object-level depth from a monocular RGB image by deforming the category-level shape prior into object-level depth and the canonical NOCS representation. Two novel modules named Normalized Global Position Hints (NGPH) and Shape-aware Decoupled Depth Reconstruction (SDDR) module are introduced to learn high fidelity object-level depth and delicate shape representations. At last, the 6D object pose is solved by aligning the predicted canonical representation with the back-projected object-level depth. Extensive experiments on the challenging CAMERA25 and REAL275 datasets indicate that our model, though simple, achieves state-of-the-art performance., Comment: Accept to ECCV 2022

Monocular 3D object detection is a fundamental but very important task to many applications including autonomous driving, robotic grasping and augmented reality. Existing leading methods tend to estimate the depth of the input image first, and detect the 3D object based on point cloud. This routine suffers from the inherent gap between depth estimation and object detection. Besides, the prediction error accumulation would also affect the performance. In this paper, a novel method named MonoSIM is proposed. The insight behind introducing MonoSIM is that we propose to simulate the feature learning behaviors of a point cloud based detector for monocular detector during the training period. Hence, during inference period, the learned features and prediction would be similar to the point cloud based detector as possible. To achieve it, we propose one scene-level simulation module, one RoI-level simulation module and one response-level simulation module, which are progressively used for the detector's full feature learning and prediction pipeline. We apply our method to the famous M3D-RPN detector and CaDDN detector, conducting extensive experiments on KITTI and Waymo Open datasets. Results show that our method consistently improves the performance of different monocular detectors for a large margin without changing their network architectures. Our codes will be publicly available at https://github.com/sunh18/MonoSIM}{https://github.com/sunh18/MonoSIM.

Recently, category-level 6D object pose estimation has achieved significant improvements with the development of reconstructing canonical 3D representations. However, the reconstruction quality of existing methods is still far from excellent. In this paper, we propose a novel Adversarial Canonical Representation Reconstruction Network named ACR-Pose. ACR-Pose consists of a Reconstructor and a Discriminator. The Reconstructor is primarily composed of two novel sub-modules: Pose-Irrelevant Module (PIM) and Relational Reconstruction Module (RRM). PIM tends to learn canonical-related features to make the Reconstructor insensitive to rotation and translation, while RRM explores essential relational information between different input modalities to generate high-quality features. Subsequently, a Discriminator is employed to guide the Reconstructor to generate realistic canonical representations. The Reconstructor and the Discriminator learn to optimize through adversarial training. Experimental results on the prevalent NOCS-CAMERA and NOCS-REAL datasets demonstrate that our method achieves state-of-the-art performance., Comment: 13 pages, 9 figures, 7 tables

We propose a highly reflective porous polymer film, fabricated by polymerization-induced phase separation (PIPS), to be integrated on the reflective cup of light-emitting diode (LED) lamps. In detail, a liquid mixture consisting of monomers of polymers, porogens and photoinitiator is used as the formulation of phase separation process. Different reflectivity is achieved by easily tuning the film thickness. With an optimized film thickness of ~55 μm, the porous polymer film features an average reflectivity of ~ 92.18% in the visible wavelength range 400-800 nm. When applied on the LED reflective cup, the porous films improve the optical efficiency of LED lamps and the angular color uniformity. The measurement results show that compared with the LED lamp without porous films, the luminous flux of the LED with porous films increases by 11.56% with the 60% weight percent of phosphor in phosphor- polydimethylsiloxane ( PDMS)layer at the current of 100 mA and the correlated color temperature deviation decreased from 34561 K to 2743 K with the 47.37% weight percent of phosphor in phosphor-PDMS layer at the current of 100 mA. Therefore, the porous polymer film made by polymerization-induced phase separation is a promising material to promote the optical performance of LED lamp.

Perovskite quantum dots (PQDs) are emerging fluorescent materials with high quantum efficiency and broad spectral tunability. Their applications on light-emitting diodes (LEDs) are promising for LED illumination & display and the rise of optical communication. However, PQDs degrade undesirably sharply in atmosphere because they are susceptible against water, oxygen and heat. Herein, we encapsulated green PQDs with micro-spheres of phase change paraffin to obtain resistance against water, oxygen and heat. We coated the micro-spheres with silicon dioxide to manufacture microcapsules to keep them in state of solid powder when paraffin melts. Finally, microcapsules are applied on LEDs as conversion layer and these LEDs show optical sensitivity to temperature.

We adopt polymerization-induced phase separation to fabricate highly scattering porous films, which serve as a diffusing reflective layer for enhancing the optical efficiency of light emitting diode lamp.

Achieving good light management is key for quantum dots (QDs) - polymer hybrid films, which are increasingly used in display and lighting applications in tandem with light emitting diodes. To overcome the insufficient absorption of blue light by the QDs and light trapping of downshifted emission, we propose an approach based on microcellular foaming in order to engineer porous hybrid films with improved green and red emission.

High-power laser illumination is considered as one of the most potential method for the next generation of lighting. However, heat accumulation greatly influences the optical performance of the phosphor converted layer, which is bottleneck of the high-power laser illumination system. In this study, a semiconductor chilling plate (SCP) with water cooling system was adopted to dissipate heat accumulated by phosphor convertor during the high-power blue laser excitation. Input laser power and the power of SCP were experimentally evaluated. The thermal and optical performances were also evaluated, respectively. As a result, the phosphor layer with a SCP showed better heat dissipation than the phosphor layer without a SCP. When the system was in the optimizing SCP substrate temperature (5℃), the highest input laser power that the phosphor layer with a SCP can sustain is 4.82W, which is 62.23% higher than the phosphor layer without a SCP (2.97W). Therefore, the phosphor layer with a SCP shows great potential in high-power laser illumination system.

Quantum-dots (QDs) have attracted great attention for their excellent advantages, but the bad reliability of heat and water limits its application. So QDs/epoxy composite particles are proposed to improve stability of QDs and serve for direct package in industry. The composite particles were mainly fabricated by mechanical grinding process, and then packaged for application. The reliability of the composite particle film shows greater performance than the pure QDs/PDMS film. Under the environment of humidity of 85% and temperature of 85℃, the luminous efficiency of the device with composite particle film rose mildly in the first 8 h and could maintain 100% after 92 h. But the luminous efficiency of the device with pure QDs/PDMS film kept decreasing with the aging time. After aging for 160 h, the luminous efficiency of the device with pure QDs/PDMS film decreased 64.1%, but the luminous efficiency of device with the composite particle film only decreased 2.5%, showing the better reliability performance. Besides, the device with composite particle film only scarifies luminous flux of 5.11% and 6.41% compared with the pure QDs/PDMS film in the same QD concentration and at similar CCT, respectively. It can be concluded that the fabrication of QDs/epoxy composite particles is a good way to improve the stability of QDs in the actual application with a small sacrifice of luminous efficiency.

The optical performance of phosphor-converted light-emitting diodes (pcLEDs) has been widely concerned. However, the phosphor particles are usually randomly distributed in the silicone to convert the blue light into yellow or red light. With the development of the precision printing and 3D printing, the phosphor particles may be precisely arranged in the near future. It indicates that the phosphor converted layer can be designed on the particle level. In order to investigated this aspect, in this work, we simulated the orthogonally and hexagonally staggered phosphor particles by finite difference time domain method. Results show that the electric field strength Poynting vector in the Z-axis direction of orthogonally staggered particles is higher than random arrangement. The output power distribution is more uniform when particles distributed randomly, and there is no obvious difference of output power between hexagonally staggered particles and random particles. But these results of the orthogonally staggered particles are higher obviously than others. These conclusions of this work can be served as a designing reference for manufacturing high-quality WLEDs.

Inspired by the porous scale of the bright white beetle Cyphochilus, a polymerization-induced phase separation method is proposed to fabricate bioinspired high-scattering polymer films with porous structures. With an optimized formulation, the porous films with a mean pore size of ∼ 200 n m feature a broadband reflectance of ∼ 71 % at a thickness of 16 µm and are measured to have a transport mean free path of ∼ 3 µ m . The porous films with high reflectivity enable the application on light-emitting diodes and have great potential in other similar optoelectronic fields.

For any positive integer k, let Ak be the Smarandachek -power product sequence. In this paper we prove that if k isan odd integer, with k> 1, then Ak contains only one prime 2.