Optical Review最新文献

To enable the operation of a mid-wave infrared (MWIR) camera under vacuum and low-temperature conditions for space-based Earth imaging optical systems, research was conducted on the optical system, mechanical structure, and vacuum and low-temperature testing methods employed in the MWIR optical system. A low-temperature MWIR camera was designed to operate under normal atmospheric pressure, vacuum, and low-temperature conditions. The camera comprises independent optical lenses, an MWIR dewar, an image processing unit, a vacuum refrigeration unit, and preset water cooling pipes. The MWIR lens consists of a front lens unit, a focusing lens unit with a two-stage reduction mechanism, and a rear lens. The assembly temperature of the MWIR camera is 293 K with an operational temperature of 100 K, and the temperature variation does not exceed 193 K. A structural thermal-optical performance analysis of the MWIR lens was conducted to evaluate the optical performance degradation caused by temperature changes. The measurement of the MWIR lens was described using an MWIR interferometer and a spherical standard MWIR mirror, providing on-axis and off-axis wave aberrations. One method was proposed to test the modulation transfer function of the MWIR camera under two different conditions. Experimental results confirmed that the overall design of the MWIR camera ensures normal operation in a vacuum low-temperature environment.

Optical fiber X-ray sensors have the potential to realize real-time dose monitoring of precision radiotherapy. However, an over-response phenomenon can occur when using an optical fiber sensor (OFXS) filled with inorganic scintillator (Gd₂O₂S:Tb) to measure the off-axis ratio (OAR) curve. The aim of this paper is to study the mechanism responsible for the over-response. Due to the complex particle distribution present in water phantoms, the Monte Carlo-based code GEANT4 was used to model the response of the scintillator. The energy response of the scintillator to photons and electrons was initially simulated, which subsequently allowed the OAR curve to be simulated and the results were compared with experiment. To analyze the energy distribution of particles in different positions, electron spectroscopy was simulated together with the photon spectrum at the position from the central axis to a distance of 14.5 cm away from the center. Finally, three metal (Al, Cu, Sn) caps were made for the OFXS to prevent the low-energy photons penetrating the OFXS, and the OARs measurements were repeated. The results show that the scintillator exhibits higher sensitivity to photons with energy below 0.5 MeV, while for electrons, the scintillator has a higher sensitivity to high-energy electrons. Simulations for electron spectroscopy and the photon spectrum show that there are many low-energy photons with relatively few low-energy electrons. The OARs measured using the OFXS with metal caps show that the over-response can be mitigated using a high-Z metal cap. The measurements demonstrate that the OAR cure measured using an OFXS fitted with a Sn cap exhibits the closest response to that measured using an IC.

The folded optics for HMD (head-mounted display), commonly referred to as pancake optics, is widely used to realize a compact HMD headset. The optics has the advantage of compactness, but also has a big drawback of lowering light efficiency. To overcome the issue, we proposed novel HMD pancake optics named “DP (double path) pancake optics” to achieve both compactness and high light efficiency simultaneously. In this paper, we introduce the principle of our “DP pancake optics” and review our prototype. We describe optical simulation results to find a highly balanced design among thickness, lens power, and magnification ratio. We also describe fabrication study of, such as polarization state and alignment accuracy. We successfully have fabricated two prototypes with 90° FOV (field of view), one of which is 20.6 mm optics thickness and the other is 25.5 mm optics thickness. The latter prototype especially shows high MTF with a 1200 ppi (pixel per inch) resolution LCD (liquid crystal display). Both prototypes have 1.8 times higher light efficiency than that of conventional one. In addition, to further expand the DP pancake optics, we also describe the improved design with wider FOV for future prototype fabrication. Therefore, we also show the optical simulation result of the improved design.

In this study, we aim to conduct real-time sensing of indoor dust concentration distribution to mitigate the airborne transmission of coronaviruses. Airborne infection, facilitated by viruses present in particulate matter, emphasizes the importance of monitoring dust concentration as an indicator of virus spread. Our approach involves the implementation of a time-synchronized wireless sensor network for real-time sensing of dust concentration distribution. The time-synchronized wireless sensor network relies on a proposed time-synchronization algorithm, ensuring a time error of less than ± 1.27 ms. This precision enables the measurement of even fast-moving dust particles. To validate the feasibility of the wireless time-synchronized sensor network, we utilized a dust ejector (air cannon) and positioned time-synchronized sensors in a row. Dust particles released from the ejector passed through each time-synchronized sensor terminal. Simultaneously, a video recording (60 frames) was conducted, and the measured times of the time-synchronized sensor terminals were compared with the lap times of the video. The results of this comparison revealed identical lap times between the time-synchronized sensor data and the video, affirming the successful operation of the time-synchronized wireless distributed sensor node as designed.

BaGeTeO₆: Nd³⁺/Yb³⁺/Ho³⁺ green up-conversion phosphors were synthesized using the high-temperature solid-state reaction method. The optimal doping concentrations for the three dopant ions Nd³⁺, Yb³⁺, and Ho³⁺ were determined to be 1 mol%, 6 mol%, and 0.8 mol%, respectively, through the method of controlling variables. By analyzing the dependence of the up-conversion luminescence intensity on the pump current of the 980 nm laser, it was found that the green and red up-conversion emissions of Ho³⁺ ions under 980 nm laser excitation were both two-photon processes. Furthermore, the influence of temperature on the up-conversion luminescent properties of BaGeTeO₆: Nd³⁺/Yb³⁺/Ho³⁺ green up-conversion phosphors under 980 nm laser excitation was investigated, and the temperature sensing properties of Ho³⁺ ions were discussed. The results indicated that, at room temperature and higher temperatures, both the red and green up-conversion emissions of the sample were two-photon processes. Within the range of excitation current used in the experiment, the ratio of red to green up-conversion luminescence intensity of Ho³⁺ ions was independent of the laser excitation current but correlated with the sample temperature. In the temperature range of 303–723 K, the ratio of red to green up-conversion luminescence intensity of Ho³⁺ ions exhibited a nonlinear relationship with temperature. Comparing the temperature sensing sensitivity of Ho³⁺ in different matrices, the results indicated that the sample possessed high temperature sensing sensitivity.

A novel design of ultrahigh efficiency and ultralow threshold energy all-optical switches based on local state transition of complete-connected optical waveguide networks (CCOWNs) is proposed. The generation of the ultra-narrow transmission peak and the ultra-strong photonic localization in network is attributed to the mutation of states, which are significant improvements in the performance of all-optical switch. First, the ultra-strong photonic localization induces the Kerr effect in nonlinear material, which transforms the transmission peaks into a transmission valley and results in the super-high efficiency. The efficiency of switch based on CCOWN with 11 unit cell (UC) and each UC possessing 7 nodes was calculated and found to be approximately (1.38 times 10^{39}), which is 13 orders of magnitude better than previously reported. Furthermore, the ultra-strong photonic localization also leads to the ultralow threshold energy. Calculations reveal that the threshold control energy of all-optical switch based on CCOWN only with 7 UC and each UC possessing 5 nodes is about (5.78 times 10^{-30}) J, which is 5 orders of magnitude smaller than the best reported results. In addition, fitting formulas for the transmission and switching efficiency with UC number have been derived, and the results show that the switching efficiency increased exponentially with the UC number and nodes. This study not only presents a new model for designing all-optical switch with outstanding performance, but also provides the possibility for further practical use of all-optical switch, while deepening our insight into optical waveguide networks.

In this paper, we use FDTD Solutions software to construct the light-absorption model of InGaAs/InP thin films modified by Au nanoparticles. And the effects of Au nanoparticles on the light-absorption performance of thin films in the near-infrared wavelengths are investigated in terms of nanoparticle position, array period, and particle radius. And for the 1064 nm wavelength band, we obtain the optimal structural model. It has been shown that nanoparticle modification on the front side of the emission layer is the most effective in promoting light absorption; the resonance peaks formed by the surface plasmon excitations can greatly affect the light-absorption rate of Au nanoparticles adsorbed on the film, and the position of the absorption peaks can be changed by altering the array period and particle radius to achieve the enhancement of the film's absorption of light in a specific wavelength band. For the 1064 nm band, we obtain the best model, when the radius of Au NPs in the emission layer is 25 nm, and the model absorption with an array period of 150 nm is up to 84.85%, and the quantum efficiency is improved by one-third compared with the thin film. It provides a certain reference for the design of photocathode in the near-infrared band.

Orthopedic surgical robots utilize near-infrared (NIR) optical locators to enable precise navigation during operations. Markers are crucial in the locator system, capturing the positions and orientations of surgical instruments and patients during operation. While spherical markers can be easily detected, they are less robust owing to limited feature points. In contrast, planar markers offer more feature points and greater resistance to occlusion. However, the demanding nature of orthopedic surgeries necessitates specific requirements for NIR-based planar markers, such as size, illumination, weight, and heat dissipation. To address these challenges, we designed an edge-lit NIR calibration board (300 mm × 300 mm) to calibrate the constructed NIR camera, with its effectiveness validated through extensive experimental studies. Based on the fundamental design data obtained from the designed edge-lit NIR calibration board, and considering the luminous flux density and the available 12 V battery on the market, we proposed an edge-lit active NIR planar marker with dimensions of 70 mm × 60 mm and equipped with eight LEDs (1.5 V, 0.085 W each). The experiential data illustrates the max relative standard deviation are around 0.93% and 0.78% for the measurement precision subjected to 10 mm × 10 mm square (5 × 5 squares) with 16 and 36 feature points, respectively. Further, we validated the following from the experimental results: (1) A 12 V 1000 mAh alkaline battery has an autonomy of approximately 16 h for the eight NIR LEDs. (2) The total heat energy conversion of 0.408 W for the marker is within acceptable limits for use in an operation room. (3) The total weight of approximately 21.6 g, including the planar marker and the selected battery, is manageable. Therefore, the designed edge-lit active NIR planar marker presents a viable option for integration into the locator system of orthopedic surgical robots.

The major concern in signal processing for holographic data storage (HDS) systems is the two-dimensional (2D) inter-symbol interference (ISI), which arises from neighboring pixels in every direction on the data page of HDS systems. Recently, serial–parallel detection has been proposed for bit-patterned media recording (BPMR). We have realized that the serial–parallel detection structure is more suitable for HDS systems than BPMR systems, because, unlike BPMR systems, the interferences in HDS systems from horizontal and vertical directions are equal. Therefore, the serial–parallel structure for HDS systems can extract better bit-error-rate performance.

Polystyrene (PS) has not been much used as an optical material due to the considerably high birefringence of PS. For the extensive use of PS in the imaging-lens systems, lower birefringence should be attained for the enhancement of the resolution. Previously, we have developed PS with extremely low birefringence (LB-PS) even when the molecular chain orientation of PS occurred. It indicates that PS may now become an effective material with excellent properties for optical lenses. In this paper, we compared the birefringence of our developed LB-PS with ones of commercial optical polymers that are most commonly utilized in imaging-lens systems. It was confirmed that the birefringence of LB-PS was comparable or even better than that of the commercial ones with high resolution. By designing an imaging-lens system, it was also confirmed that employing PS with the Abbe number of 31.5 could be highly effective in compensating for chromatic aberration as well as obtaining high optical resolution. Moreover, the resolution performance of several lens systems was calculated, analyzed, and compared by considering the birefringence of cyclo-olefin polymer (COP), normal PS, and LB-PS. It was found that LB-PS could maintain high resolution, while normal PS with high birefringence exhibited significant decrease in resolution. It was also found that LB-PS generated higher resolution than COP. All these results revealed that LB-PS could be an excellent optical material to compensate for the chromatic aberration of lens systems, leading to the enhancement of the actual resolution performance. It was, therefore, expected that LB-PS could contribute to improving the resolution performance of smartphone cameras and security cameras.