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Optical properties of blueberry flesh and skin and Monte Carlo multi-layered simulation of light interaction with fruit tissues
摘要： One of the major issues of fresh blueberry production is the excessive bruising caused by mechanical impact during harvesting and packaging, which substantially lowers fruit quality and therefore compromises consumer satisfaction as well as the profitability for growers. Spectroscopy and imaging techniques such as hyperspectral imaging have great potential to detect and quantify internal bruises in fruit. It is important to measure the fundamental optical properties of blueberry tissues to better employ spectroscopy or imaging techniques. The aim of this study was to obtain the absorption coefficient (μa), reduced scattering coefficient (μs'), and scattering anisotropy (g) of blueberry flesh and skin in the spectral regions of 500–800 nm and 930–1400 nm and investigate the light propagation model of blueberries using Monte Carlo multi-layered (MCML) simulation. The total reflectance, total transmittance, and collimated transmittance of blueberry flesh and skin with three treatments (non-bruised, 30-min bruised, and 24-h bruised) were collected using a single integrating sphere-based spectroscopic system. Using the collected spectra, the inverse adding-doubling (IAD) method was applied to calculate μa, μs', and g. Results indicated that the differences between bruised (30 min and 24 h) and non-bruised flesh samples for both μs' and g were significant from 930 nm to 1400 nm. Microscope images revealed that the differences were caused by the damaged and ruptured cellular structure of bruised flesh. Although μa, μs', and g showed significant differences between non-bruised and bruised (30 min and 24 h) flesh in the spectral region of 400–700 nm, the MCML simulation results showed that this spectral region is not effective in detecting bruises due to strong absorption and backward scattering of the blueberry skin. In contrast, the absorption effect of the skin in the near infrared range (930–1400 nm) was small, allowing light to penetrate and interact with the flesh. Therefore, the near infrared spectral region is an effective spectral range for inspecting bruised blueberries using either reflectance or transmittance method. This study reported the optical properties of blueberry skin and flesh with varying degree of bruising for the first time and simulated photon interaction with fruit tissues for bruising detection using MCML. These findings would provide guidance to develop non-destructive sensing methods for blueberry internal bruising detection.
关键词： Bruising detection,Integrating sphere,Inverse adding-doubling (IAD)
更新于2025-09-23 15:22:29
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Study on Nitrogen-Doped Graphene Ink and Its Effects on the Heat Dissipation for the LED Lamps
摘要： This study explored the application of nitrogen-doped graphene (NDG) ink to the coating of light-emitting diode (LED) lamps for the thermal management. Unlike the general solutions of graphene, the NDG ink used in this study was tuned with high electrical resistance and quietly suitable for the application of the LED lamp coating, which prevented the short circuit problem; besides, the NDG ink also provided a high heat dissipation effect to improve the performance of the LED lamp. The investigation of adhesion and resistance for the NDG ink were conducted by the cross-cut test and the four-point probe resistance measurement, respectively. Three types of LED lamps including the original lamp, fin-removed lamp, and NDG-ink coated (NGC) lamp were tested for the actual operating temperature distribution by K-type thermal couples and for the lumens by the integrating sphere. The results showed that the heat dissipation of the NGC lamp was better than that of the original lamp. In addition, the inspections for the properties of NDG powder were also performed by x-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and Raman spectroscopy. According to the inspectional results, the NDG powder had a percentage of nitrogen of about 3.8% by XPS, a surface roughness Rq of 0.9 nm by AFM, and over ten layers by Raman analysis. It showed that the NDG powder in this study belonged to the type of multi-layer graphene.
关键词： integrating sphere,heat dissipation,nitrogen-doped graphene,LED
更新于2025-09-23 15:19:57
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Spectral responsivity calibration of a polarization remote sensor based on a supercontinuum laser and monochromator
摘要： Relative spectral responsivity is a basic parameter for detecting and evaluating the in-band response non-consistency of the channel polarization remote sensor (CPRS) in laboratory calibration. In this paper, a spectrally resolved calibration facility was assembled for the calibration of relative spectral responsivity by using novel supercontinuum laser and monochromator (SLM). Taking three polarization channels of 490 nm, 670 nm and 910 nm as examples, the relative spectral responsivity of the CPRS was obtained from two calibration sources, respectively – the SLM and the monochromatic light from SLM steered into integrating sphere. Before measuring the relative spectral responsivity of the CPRS, the degree of linear polarization (DOLP) and the polarization orientation angle of two calibration sources were acquired by the spectral polarization analyser (SPOLA). The test result indicates that the output light of the latter calibration source has less the DOLP and smaller range of variation in the polarization orientation angle. In the experiment of measuring the relative spectral responsivity, while using monochromator as calibration source, the in-band response non-consistency of the three channels were 0.91%, 4.25% and 1.06%, respectively. Correspondingly, while using monochromatic light steered into integrating sphere, there were 0.15%, 0.47% and 0.57%, respectively. It can be concluded that SLM equipped integrating sphere sharply decreased the impact from the polarization characteristic of the source and could be e?ectively applied in the relative spectral responsivity calibration of CPRS.
关键词： spectral responsivity,integrating sphere,monochromator,supercontinuum laser,polarization remote sensor
更新于2025-09-19 17:13:59
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Measurements of High Power Levels of Laser Radiation by Pass-Through Receivers
摘要： The problem of developing measuring instruments for high levels of laser power of the pass-through type was posed and solved. Methods for solving the problem are presented. A measuring instrument has been developed, in which a two-step circuit design is applied for power attenuation of the laser beam to an operating level as measured by the radiation detector. It is shown that due to the original design of the attenuation steps and their arrangement in relation to the laser beam it is possible to achieve values of the attenuation coefficient of (0.2–0.4)·1010 and to measure power up to 10–15 kW without forced cooling of elements of the measuring instrument. Application of the design of steps makes it possible to reduce the dimensions of the measuring instrument and pass practically all radiation to the output without changing the characteristics of the initial laser beam. The measuring instrument that was developed differs from known analogs and is suitable for work with process lasers. For reliable measurement of laser radiation power, the conditions were determined for selecting the time constant of integration of the radiation detector. The connection between the time constant of integration of the radiation detector and the geometrical characteristics of the measuring instrument is shown.
关键词： attenuator,reflector,integrating sphere,laser power,attenuation coefficient
更新于2025-09-12 10:27:22
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[IEEE 2019 International Conference on Opto-Electronics and Applied Optics (Optronix) - Kolkata, India (2019.3.18-2019.3.20)] 2019 International Conference on Opto-Electronics and Applied Optics (Optronix) - Design of High-Performance LED Based Integrating Sphere for Illumination & Communication
摘要： An integrating sphere has been specially designed using multiple white light LEDs mounted on both the inner and outer surfaces of the sphere to create improved uniform illumination inside a computer laboratory room. The LEDs are simultaneously used as optical transmitters of trans-receiver systems for indoor optical wireless communication. More uniformity of light helps to develop better access to wireless communication systems, comfortable movement inside the room and reduced shadowing effect in wireless communication. One integrating sphere fitted with LED arrays divided among outer and the inner surfaces of the sphere is able to create ideal uniformity conditions for illumination and data communication within a volume (3 x 3 x 3) m3 of laboratory space. The system is capable of bidirectional full-duplex communication using IR LEDs as source for uplink and silicon photodiodes as receivers for optical wireless communication links. The theory and the design principles of the integrating sphere and the optical wireless communication link design would be presented.
关键词： integrating sphere,optical communication,wireless communication,uniform illumination,white light LED
更新于2025-09-11 14:15:04
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Calibration of the Pyranometer Sensitivity Using the Integrating Sphere
摘要： The pyranometer for observing the solar radiation reaching the surface of the earth is manufactured by various companies around the world. The sensitivity of the pyranometer at the observatory is required to be properly controlled based on the reference value of the World Radiometric Center (WRC) and the observatory environment; otherwise, the observational data may be subject to a large error. Since the sensitivity of the pyranometer can be calibrated in an indoor or outdoor calibration, this study used a CSTM-USS-4000C Integrating Sphere by Labsphere Inc. (USA) to calibrate the sensitivity of CMP22 pyranometer by Kipp&Zonen Inc. (Netherlands). Consequently, the factory sensitivity of CMP22 was corrected from 8.68 μV·(Wm?2)?1 to 8.98 μV·(Wm?2)?1, and the result from the outdoor calibration according to the observatory environment was 8.90 μV·(Wm?2)?1. After the indoor calibration of the pyranometer sensitivity, the root mean square error (RMSE) of the observational data at the observatory on a clear day without clouds (July 13, 2017) was 7.11 Wm?2 in comparison to the reference pyranometer. After the outdoor calibration of the pyranometer sensitivity based on these results, the RMSE of the observational data was 1.74 Wm?2 on the same day. Periodic inspections are required because the decrease of sensitivity over time is inevitable in the pyranometer data produced at the observatory. The initial sensitivity after indoor calibration (8.98 μV·(Wm?2)?1) is important, and the sensitivity after outdoor calibration (8.90 μV·(Wm?2)?1) can be compared to the data at the Baseline Surface Radiation Network (BSRN) or can be used for various studies and daily applications.
关键词： Sensitivity,Pyranometer,Solar radiation,Indoor?outdoor calibration,Integrating sphere
更新于2025-09-10 09:29:36
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Photoluminescence of the integrating sphere walls, its influence on the absolute quantum yield measurements and correction methods
摘要： Determination of the absolute quantum yield (QY) of photoluminescence (PL) or electroluminescence is commonly performed using an integrating sphere (IS) – versatile device for radiometry applications. The key feature of IS is very high diffused reflectance of its internal surface. Two materials are commonly used: (a) the sintered high-density polytetrafluoroethylene (Spectralon) and (b) materials based on barium sulphate (Spectrafect). Using PL-micro-spectroscopy we show that both materials reveal PL from localized centers excitable by UV, blue and green light emitting broad PL spectrum extending up to the red spectral region. The main effect of PL from IS-walls is introduction of non-constant parasitic background which is mixed with PL from a tested sample during the QY measurements. We develop theoretical description of QY determination which includes effects of PL from IS walls. This allows us to propose and test a reliable and universal correction for the IS-related PL background. Finally, a method of “black sample” is proposed and applied to estimate PL QY of Spectrafect which is shown to decrease from 0.09 to 0.015% for excitation shift from 320 to 440 nm.
关键词： photoluminescence,integrating sphere,Spectrafect,Spectralon,quantum yield
更新于2025-09-09 09:28:46