Lamp Array Research Articles

Inverse problem for thermal radiation distribution on turbine blade under quartz lamp irradiation

Due to the strong time-varying characteristics and complex geometry of aerospace components, rapid changes in the distribution of radiative heat flux on the test surface are often required during non-uniform aerodynamic heating tests. However, it takes time to adjust the geometric parameters of the lamp array, which cannot meet the requirement for rapidly changing radiative heat flux distribution. To address this issue, a new method for calculating radiant heat flux and a fast linear analysis method of quartz lamp power are proposed which can calculate radiant heat flux distribution of complex surface and meet the need of timeliness and rapidity in radiant heat flux distribution, making it more suitable for engineering applications. Through numerical verification under single lamp and quartz lamp array, the maximum difference between the theoretical analysis method and the Monte Carlo method is less than 2.25% under single lamp, and less than 5% under quartz lamp array. Finally, turbine blade model and plane model are taken as research objects to verify the feasibility and reliability of the fast linear analysis method of quartz lamp power. The results show that the relative average error of the calculated quartz lamp power is 5.86% and 14.83%, respectively, compared with the actual power. This provides a reference and basis for the rapid simulation design of thermal radiation environment during the experiment.

A Novel Compact GNSS Antenna with Plasma Frequency Selective Surface

In this study, a plasma frequency selective surface (PFSS) was designed with an array of ordinary fluorescent lamps backed by a conducting plate. The proposed PFSS structure was used as a reflector with the spiral two arms Archimedean type Global Navigation Satellite System (GNSS) antenna to reduce the overall size of the antenna system. Characteristics and the performance of the proposed system were presented by using the results of simulations and experiments in the GNSS band. The optimum distance between antenna and PFSS was found to be around 35 mm to achieve a maximum gain in the simulation which is a lower profile than antenna with conventional conductive plate (66 mm at the GNSS center frequency). Experimental results show that the antenna system has mean values of around 6.7 dBiC gain, 1.27 dB axial ratio and less than -10 dB return loss in the range of 1.14 and 1.61 GHz. All these results show that the proposed novel antenna system is suitable for the reception of the GNSS signals with the advantage of its low profile design.

Ultra‐High Peak Power Generation for Rotational Triboelectric Nanogenerator via Simple Charge Control and Boosted Discharge Design

AbstractCurrently, enhancing the output power of rotational‐mode triboelectric nanogenerators (TENGs) using various complicated systems is a contentious issue; however, this is a challenging process owing to the inherent characteristics of TENGs, namely, low output currents as opposed to high voltages. Thus, this study proposes a simple and innovative strategy for ultra‐high output peak power generation of TENGs called a self‐boosted rotational electrostatic‐discharge TENG (SRE‐TENG). The SRE‐TENG mechanism is unique as it is based on charge control and boosted discharge design, thereby achieving a remarkable peak power of 1103.8 W, peak power density of 140.6 Kw m−2, low optimum resistance of 100 Ω, and broad peak power generation range of 10 Ω to 1 GΩ. Diligent measurements and analyses of the peak and root‐mean‐square voltage and current outputs of the SRE‐TENG are conducted for various design variables and circuit configurations. The proposed SRE‐TENG mechanism is validated using experimental and multiphysics simulation results. The high‐output performance of the SRE‐TENG is demonstrated via the lighting of 3,000 LEDs and a 60‐W lamp array, continuous driving of a commercial sensor array, and hydrogen/oxygen generation via water electrolysis.

Improving inactivation performance of in-duct ultraviolet germicidal irradiation system with ribbed duct walls by optimizing UVC distribution

The in-duct ultraviolet germicidal irradiation system (ID-UVs) with ribs has been revealed to be effective in reducing the risk of biological contamination, and optimization of its UV radiation distribution is expected to further improve the inactivation performance. In this study, the Critical Survival Fraction Probability (CSFP) and Maximal Bearable UVC Dose (MBUD) methods were synergistically employed as evaluation indicators, and Computational Fluid Dynamics (CFD) was used to optimize the lamp array, duct shape, liner reflectivity and number of UV lamps. Results indicated that the optimal lamp array was positioned at 0° to the airflow direction, and square-section ducts were preferred over circular-section ducts. Ribs obstructed the transmission of specular reflected radiation, while diffuse reflection helps to overcome the obstruction. Reducing the number of lamps alone from four to one increased the volume-averaged irradiance by 14.4–25.3 % in the main irradiated region. For renovation projects, ID-UVs equipped with one lamp and galvanized steel ribs proved optimal, exhibiting increased inactivation efficiencies of 39.7 % (CSFP) and 239.4 % (MBUD) against highly UVC-susceptible MS2 Bacteriophage (K = 0.038 J/m2), and up to 341.1 % (MBUD) against low UVC-susceptible MS2 Bacteriophage (K = 0.028 J/m2) compared to the ID-UVs without ribs and featuring four lamps. Moreover, in comparison to conventional conditions that provide equivalent air-cleaning levels, the optimal ID-UVs allowed for a 60–70 % increase in air handling capacity while achieving at least an 83.6 % reduction in annual energy costs. These findings contribute towards advancing practical applications of ID-UVs with ribbed duct walls.

First- and second-order phase transitions in electronic excitable units and neural dynamics under global inhibitory feedback

The diverse roles of inhibition in neural circuits and other dynamical networks are receiving renewed interest. Here, it is shown that increasing global inhibitory feedback leads to gradual rounding of first-order transition between dynamical phases, turning it into second-order transition. The effect is initially observed in an electronic model consisting of a bi-dimensional array of neon glow lamps, where global inhibition can be simply introduced through a resistor in series with the supply voltage. The experimental findings are confirmed using both an extended numerical model and a mean-field approximation, then replicated across different models of neural dynamics, namely, the Wilson–Cowan model and a network of leaky integrate-and-fire neurons. Across all these systems, a critical point is always found as a function of a pair of parameters controlling local excitability and global inhibition strength, and a general explanation revealing the roles of the shape of the activation function and voltage fluctuations versus the extinction time-scale is provided. It is speculated that the brain could use global inhibition as a versatile means of shifting between first- and second-order dynamics, addressing the conundrum regarding the coexistence in neural dynamics of phenomena stemming from both. Some reflections regarding the comparison with other physical systems and the possible physiological significance are offered, and a hypothetical setup for an optogenetics experiment on cultured neurons is put forward.

Development of Rotary Solar Receiver and Solar Simulator Facility for Concentrated Solar Power Applications

A prototype rotary solar receiver and a solar simulator facility have been designed, built and commissioned by Odqa Renewable Energy Technologies in conjunction with The Oxford Thermofluids Institute, University of Oxford for the validation of concentrated solar power technologies. The key features of the rotary solar thermal receiver include the rotating absorber surface which incorporates a high temperature heat transfer design. The innovative design also includes a compact solar power inlet aperture for very high incident heat flux to reduce the radiant heat loss from the high temperature surface. Air is used as the heat transfer fluid as this has system integration advantages over other types of heat transfer media, such as CO2, steam, molten salt, or solid particles. A 30kWe Xenon-arc lamp high heat flux incident light has also been developed to enable experimental validation of the solar receiver technologies. The Xenon-arc lamp array consists of three lamps combined with a custom designed, 5-degree-of-freedom focusing mechanism to achieve precise focus and maximise the heat flux. The receiver has successfully produced working fluid temperatures reaching 1200°C, demonstrating the concept viability for high temperature processes.

Characterization and Deviation Analysis of a High-Flux Solar Simulator With Metal-Halide Lamps

Abstract Utilizing highly concentrated solar power for thermochemical processing as one of the extraterrestrial in situ resource utilization (ISRU) applications has been highlighted as an essential technique to support deep-space exploration in the future. Multi-source high-flux solar simulators (HFSSs) are widely employed to provide stable irradiance for indoor solar thermal experiments. Meanwhile, numerical modeling that can characterize the radiation transport mechanisms within the solar thermal system has been developed for performance evaluation before field trials. However, significant differences between simulated and measured flux distributions were shown for existing models developed based on the Monte-Carlo ray-tracing (MCRT) method, which has been attributed to only one or two specific reasons. In this paper, we proposed a comprehensive analysis of the concentration characteristics of a 42 kW metal-halide lamp HFSS, developed at Swinburne University of Technology, considering the effect of five aspects. The flux distribution, uniformity, and vector distribution under different configurations were compared to quantify the influence of these factors on receiving irradiance. The suitable arc size, reflector shape, and reflector surface properties of the existing HFSS have also been numerically determined to improve the model and reduce the root mean square error (RMSE) for the lamp array from 38.2% to 8.3%. This research provides a potential pathway to numerically predict the radiation transfer performance of HFSSs and determine the suitable configuration for desired solar thermochemical applications.

Ultra-High-Sensitivity and -Stability Thin-Film Heat Flux Sensor Based on Transverse Thermoelectric Effect

In this study, we investigate the sensitivity properties of YBa2Cu3O7-δ thin films with a 15° tilting angle in relation to heat flux density. The films were prepared using the laser pulsed deposition (PLD) technique, and their characteristics were evaluated using various techniques, including X-ray diffraction (XRD), transmission electron microscopy (TEM), atomic force microscopy (AFM), and infrared steady-state and laser transient calibration systems. The YBa2Cu3O7-δ films prepared in this study were found to be of good quality, exhibiting a single-phase structure with strict (001) orientation. Both the substrate and film diffraction peaks were sharp and consistent with the step-flow growth mode, indicating high crystalline quality. Ultra-high sensitivity in the range of 0 to 100 kW/m2, the maximum sensitivity is 230 μV/(kW/m2), and an uncertainty is only 3%. According to the infrared steady-state heat flux calibration system test, when the single output power of the quartz lamp array is 0.2 kW, 0.3 kW, 0.4 kW and 0.5 kW, the maximum output voltage is 0.19 mV, 0.41 mV, 0.63 mV and 0.94 mV, respectively, indicating that the output voltage of the sensor increases with the increase in heat flux, showing a good linear characteristic, and the fitting linearity is 0.99. Through the test of the laser transient thermal current calibration system, the sensors are found to have excellent response–recovery characteristics at 500 kHz and 1000 kHz fiber laser frequencies, and the maximum voltage output is 8.83 mV and 9.09 mV, respectively. Moreover, the component has excellent repeatability, and the maximum measurement error is only 1.94%. Our findings demonstrate the potential of YBa2Cu3O7-δ thin films for use in heat flux sensing applications.

Preparation of large-scale uniformly crystallized ITO thin films by rapid infrared annealing technique

This paper proposes three engineering application technology applications for rapid infrared annealing (RIA): scanning annealing, lamp array preheating and scanning annealing, and lamp array annealing. For the dynamic scanning annealing method, the influence of the working distance from the infrared lamp to the amorphous indium tin oxide (ITO) film and the scanning speed on the heating of the film surface were studied. For lamp array preheating and scanning annealing, the attenuation of the compressive stress on the surface of the chemically strengthened glass under the condition of low temperature and the long holding time were revealed. For lamp array annealing, the influence of this technology on the optical and electrical properties of the ITO film and the surface compressive stress of chemically strengthened glass were studied. Using the lamp array preheating and scanning annealing and lamp array annealing technology, not only a crystalline ITO film with excellent optical and electrical properties and uniformity can be prepared quickly, but also the impact of the crystallization process on chemically strengthened glass can be reduced greatly.

Distribution of radiation heat flux on a plane receiver produced by a multi-quartz lamps heating system for thermal-structural tests

High heat flux generated by quartz lamps can be employed to provide a simulated aerodynamic heating environment for thermal-structural tests on spacecraft. To provide a general numerical solution for radiant heating problems and to investigate the properties of radiation heat flux distributions generated by quartz lamp heaters, a quartz lamp array radiation model is proposed based on Monte Carlo method (MCM). The performance of this numerical model, including result uncertainty and computation time, has been examined. The model is validated through the design and execution of experiments under various radiation intensities. Good agreements between the numerical and experimental results indicates the accuracy and stability of the numerical model for predicting radiation heat flux over a target plane. Then, the impact of various factors on the uniformity and efficiency of radiation dispersal are explored. The results indicate that increasing heater-receiver distance is an efficient strategy for improving radiation uniformity. The reflector is a crucial device for increasing heater efficiency. The edge effect reduces the heat flux within a 10 cm radius of filament ends. A neighboring lamp interval of less than 5 cm is an excellent choice for avoiding radiation troughs and increasing the heater's efficiency.

Study on the Thermal Distribution Characteristics of a Molten Quartz Ceramic Surface under Quartz Lamp Radiation.

More and more researchers are studying the heat transfer performance of aeronautical materials at high temperatures. In this paper, we use a quartz lamp to irradiate fused quartz ceramic materials, and the sample surface temperature and heat flux distribution were obtained at a heating power of 45~150 kW. Furthermore, the heat transfer properties of the material were analyzed using a finite element method and the effect of surface heat flow on the internal temperature field was investigated. The results show that the fiber skeleton structure has a significant effect on the thermal insulation performance of fiber-reinforced fused quartz ceramics and the longitudinal heat transfer along the rod fiber skeleton is slower. As time passes, the surface temperature distribution tends to stability and reaches an equilibrium state. The surface temperature of fused quartz ceramic increases with the increase in the radiant heat flux of the quartz lamp array. When the input power is 5 kW, the maximum surface temperature of the sample can reach 1153 °C. However, the non-uniformity of the sample surface temperature also increases, reaching a maximum uncertainty of 12.28%. The research in this paper provides important theoretical guidance for the heat insulation design of ultra-high acoustic velocity aircraft.

Effects of Nighttime Applications of Germicidal Ultraviolet Light upon Powdery Mildew (Erysiphe necator), Downy Mildew (Plasmopara viticola), and Sour Rot of Grapevine.

Nighttime applications of germicidal ultraviolet were evaluated as a means to suppress three diseases of grapevine. In laboratory studies, UV-C light (peak 254 nm, FWHM 5 nm) applied during darkness strongly inhibited the germination of conidia of Erysphe necator, and at a dose of 200 J/m2 germination was nil. Reciprocity of irradiance and duration of exposure with respect to conidial germination was confirmed for UV-C doses between 0 and 200 J/m2 applied at 4 or 400 seconds. When detached grapevine leaves were exposed during darkness to UV-C at 100 J/m2 up to 7 days before they were inoculated with zoospores of Plasmopara viticola, infection and subsequent sporulation was reduced by over 70% compared to untreated control leaves, indicating an indirect suppression of the pathogen exerted through the host. A hemicylindrical array of low-pressure discharge UV-C lamps configured for trellised grapevines was designed and fitted to both a tractor-drawn carriage and a fully autonomous robotic carriage for vineyard applications. In 2019, in a Chardonnay research vineyard with a history of high inoculum and severe disease, weekly nighttime applications of UV-C suppressed E. necator on leaves and fruit at doses of 100 and 200 J/m2. In the same vineyard in 2020, UV-C was applied once or twice weekly at doses of 70, 100, or 200 J/m2, and severity of E. necator on both leaves and fruit was significantly reduced compared to untreated controls, and twice-weekly applications at 200 J/m2 provided suppression equivalent to a standard fungicide program. None of the foregoing UV-C treatments significantly reduced the severity of P. viticola on Chardonnay vines compared to the untreated control in 2020. However, twice-weekly applications of UV-C at 200 J/m2 to the more downy mildew-resistant Vitis interspecific hybrid cultivar Vignoles in 2021 significantly suppressed foliar disease severity. In commercial Chardonnay vineyards with histories of excellent disease control in Dresden, NY, E. necator remained at trace levels on foliage and was nil on fruit following weekly nighttime applications of UV-C at 200 J/m2 in 2020, and after weekly or twice-weekly application of UV-C at 100 or 200 J/m2 in 2021. In 2019, weekly nighttime applications of UV-C at 200 J/m2 also significantly reduced the severity of sour rot, a decay syndrome of complex etiology, on fruit of the Vitis interspecific hybrid cultivar 'Vignoles', but not the severity of bunch rot caused by Botrytis cinerea. A similar level of suppression of sour rot was observed on Vignoles vines treated twice-weekly with UV-C at 200 J/m2 in 2021. Nighttime UV-C applications did not produce detectable indications of metabolic abnormalities, phytotoxicity, growth reduction, or reductions of fruit yield or quality parameters, even at the highest doses and most frequent intervals employed.

Average signal-to-noise ratio maximization for an intelligent reflecting surface and angle diversity receiver jointly assisted indoor visible light communication system.

The intelligent reflecting surface (IRS) and angle diversity receiver (ADR) jointly assisted indoor visible light communication (VLC) system is proposed to improve average signal-to-noise ratio (ASNR) performance. Specifically, to maximize the ASNR at the receiving plane, the roll angle and yaw angle of IRS and the inclination angle of the side detector in the ADR structure are optimized simultaneously as one non-convex problem. With the bat algorithm, the optimal solution is numerically obtained. Results show that when the transmit power of the light emitting diode lamp array is 1W, the ASNRs of this VLC system optimized by IRS and ADR are approximately 7.89dB, 3.58dB, and 2.09dB higher than those of the original, IRS-assisted, and ADR-assisted VLC systems, respectively. Furthermore, the transmission rate and bit error rate performances of the original, IRS-assisted, ADR-assisted, and IRS and ADR jointly assisted indoor VLC systems are also simulated and compared; it is found that the performance improvement of the indoor VLC system jointly optimized by IRS and ADR is more evident than that of the other three VLC systems. This study will benefit the research and development of indoor VLC systems.

Light-triggered oxidative activity of chromate at neutral pH: A colorimetric system for accurate and on-site detection of Cr(VI) in natural water

Hexavalent chromium (Cr(VI)), a confirmed human respiratory carcinogen, has attracted widespread attention due to its high toxicity and mobility in natural water systems. However, the developed catalytic colorimetric probes for Cr(VI) detection remain challenging, such as various species of Cr(VI) coexisting in water or acid buffer, the obvious interference from oxidizing ions at acidic pH, the synthesis of complex materials, and the consumption of hydrogen peroxide. In this work, a phenomenon of UV light-triggered chromate to produce singlet oxygen under neutral pH was found. An environmentally-friendly method based on the rapid oxidation of chromogenic substrates was thus developed for the highly specific and accurate detection of Cr(VI). Cr(VI) serves as both the active center and the target of this system, which ensures the rapidity, simplicity, and environmental protection of the proposed colorimetric strategy. Importantly, the neutral catalytic condition ensures that the predominant species CrO42- can be accurately quantified and avoids the interference of oxidizing ions. Subsequently, a portable analytical system integrating an array of LED lamps, a miniature color reading device, and a developed smartphone-based program was successfully developed to accomplish high-throughput and on-site analysis of Cr(VI) in natural water. The proposed method provides a rapid screening and water quality assessment tool for the faster, more cost-effective, and accurate detection of Cr(VI) in the water system.

Rapid die preheating using a high-power infrared lamp array

• Preheating HPDC dies for automotive transmission components was investigated. • Radiation heat transfer into HDPC dies was simulated using the Monte Carlo method. • Heater configuration was optimized to increase heat rate while minimizing hot spots. • Radiation shield was effective in minimizing hot spots on protruding surfaces. High pressure die casting (HPDC) is a highly violent process that causes significant wear on the die from chemical attacks and from repeated cycling at high pressure and temperature. In practice, HPDC dies are usually preheated by injecting aluminum into the die as warm-up shots. Although warm-up shots transfer heat into the die at a high rate, the warm-up shots are often rejected as scrap due to defects caused by the lower-than-optimal die temperature. The present work aims to develop an auxiliary heating system using an array of high-power, electric infrared lamps to preheat an HPDC die. The potential advantage of this method is a reduction in scrap material and a reduction in thermal cycles on the casting die. Experiments were conducted to quantify the heating rate for various infrared electric heater configurations. A numerical model was also developed to simulate the radiation heat transfer from the lamp array to the die. The model was validated against experiments and subsequently used to optimize the configuration of the heater. The heating system was improved by adding a small radiation shield to minimize hot spots on protruding surfaces while still maintaining a fast heating time. The validated numerical model can be used in the future to develop custom heater solutions for different die geometries.

Design, Construction, and Evaluation of Equipment for Nighttime Applications of UV-C for Management of Strawberry Powdery Mildew in Florida and California

We designed and constructed two tractor-drawn ultraviolet-C (UV-C) lamp arrays housed in hemicylindrical hulls adapted to two widths of raised bed planting systems for strawberry. Onboard UV dosimeters were fitted to the arrays to monitor UV-C output in field studies to suppress strawberry powdery mildew. Nighttime applications of UV-C were evaluated in replicated-plot field plantings in Florida and in California. Suppression of powdery mildew by nighttime applications of UV-C at 200 J m−2 was equivalent to that provided by weekly fungicide applications in California and superior to that provided by fungicide treatments in Florida. Costs of construction and operation of the UV-C apparatus were estimated to allow comparisons to conventional fungicide-based suppression of disease. UV-C applications had no negative effects on yield nor any visual phytotoxic effect on plants or fruit throughout the season. The results confirm and expand upon previously published studies involving UV-C applications in different environments.

Software-defined cooking using a microwave oven

Despite widespread popularity, today's microwave ovens are limited in their cooking capabilities, given that they heat food blindly, resulting in a nonuniform and unpredictable heating distribution. We present software-defined cooking (SDC), a low-cost closed-loop microwave oven system that aims to heat food in a software-defined thermal trajectory. SDC achieves this through a novel high-resolution heat sensing and actuation system that uses microwave-safe components to augment existing microwaves. SDC first senses the thermal gradient by using arrays of neon lamps that are charged by the electromagnetic (EM) field a microwave produces. SDC then modifies the EM-field strength to desired levels by accurately moving food on a programmable turntable toward sensed hot and cold spots. To create a more skewed arbitrary thermal pattern, SDC further introduces two types of programmable accessories: A microwave shield and a susceptor. We design and implement one experimental test bed by modifying a commercial off-the-shelf microwave oven. Our evaluation shows that SDC can programmatically create temperature deltas at a resolution of 21°C with a spatial resolution of 3 cm without the programmable accessories, and 183°C with them. We further demonstrate how an SDC-enabled microwave can be enlisted to perform unexpected cooking tasks: Cooking meat and fat in bacon discriminatively and heating milk uniformly.

Optical Attenuators Extend Dynamic Range but Alter Angular Response of Planar Ultraviolet-C Dosimeters.

Effective ultraviolet-C (UV-C) decontamination protocols of N95 respirators require validation that the entire N95 surface receives sufficient dose. Photochromic indicators (PCIs) can accurately measure UV-C dose on nonplanar surfaces, but often saturate below doses required to decontaminate porous, multilayered textiles like N95s. Here, we investigate the use of optical attenuators to extend PCI dynamic range while maintaining a near-ideal angular response-critical for accurate measurements of uncollimated UV-C. We show analytically that tuning attenuator refractive index, attenuation coefficient, and thickness can extend dynamic range, but compromises angular response unless the attenuator is an ideal diffuser. To investigate this tradeoff empirically, we stack PCIs behind model specular (floated borosilicate) and diffuse (polytetrafluoroethylene) attenuators, characterize the angular response, and evaluate on-N95 UV-C measurement accuracy within a decontamination system. Both attenuators increase PCI dynamic range >4×, but simultaneously introduce angle-dependent transmittance, which causes location-dependent underestimation of UV-C dose. PCI-borosilicate and PCI-polytetrafluoroethylene stacks underreport true on-N95 dose by (1) 14.7% and 3.6%, respectively, when near-normal to the source lamp array, and (2) 40.8% and 19.8%, respectively, in a steeply sloped location. Overall, we demonstrate that while planar attenuators can increase PCI dynamic range, verifying near-ideal angular response is critical for accurate UV-C measurements.

Use of Ultraviolet Light to Suppress Powdery Mildew in Strawberry Fruit Production Fields.

We designed and deployed an apparatus to apply UV light for suppression of powdery mildew in open field production of strawberry. The unit was evaluated in a commercial production field for one season, and for two additional seasons in open field research plots at the University of Florida Gulf Coast Research and Education Center. The apparatus contained two 180-cm-long hemicylindrical arrays of twenty 55-W low-pressure discharge UV-C lamps (operated at 30 W; peak wavelength = 254 nm) backed by polished aluminum reflectors covering two adjacent beds of the strawberry planting. The lamp arrays were suspended within a steel carriage that was tractor-drawn through the planting at 2.3, 4.6, and 5.6 km h-1. Nighttime applications of UV-C at doses ranging from 65 to 170 J⋅m-2 either once or twice weekly provided suppression of foliar and fruit disease that was consistently equal to or better than that provided by a commercial calendar-based fungicide spray program.

Optimization of location, power allocation and orientation for lighting lamps in a visible light communication system using the firefly algorithm.

To optimize the uniformity of signal-to-noise ratio (SNR) distribution in a visible light communication (VLC) system, the firefly algorithm is improved for joint optimization of location, power allocation and orientation of a light-emitting diode (LED) lamp array. Taking 16 LED lamps as an example, optimizations with a different number of degrees-of-freedom (DOF) are investigated. The orientation-involved optimizations significantly decrease average SNR and average illuminance. However, if the average illuminance is restricted to a large value, the effects of the orientation DOF would be small. With the restriction of illuminance, the optimization with all the three DOFs gives an improvement of 4.18 times in SNR uniformity, compared to the typical square-circle layout. The optimizations are further studied by varying the number of LED lamps.