Modeling and Verifying the Polarizing Reflectance of Real-World Metallic Surfaces
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Using measurements of real-world samples of metals, the proposed approach verifies predictions of bidirectional reflectance distribution function (BRDF) models. It employs ellipsometry to verify both the actual polarizing effect and the overall reflectance behavior of the metallic surfaces.Keywords:
Ellipsometry
Parameters like the sun angle as well as the measurement angle mostly are not taken into account when simulating because their influence on the reflectivity is weak. Therefore the impact of a changing measurement and illumination angle on the reflectivity is investigated. Furthermore the impact of humidity and chlorophyll in the scenery is studied by analyzing reflectance spectra of different vegetative background areas. It is shown that the measurement as well as the illumination angle has an important influence on the absolute reflection values which raises the importance of measurements of the bidirectional reflectance distribution function (BRDF).
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The bi-directional reflectance distribution function (BRDF) describes the appearance of a material by its interaction with light. In this study, Lafortune BRDF model is fitted to densely sampled measured BRDF data by using Levenberg — Marquardt Algorithm. The obtained results are visualised by a physically based ray tracing software and the proposed method is analysed.
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Using measurements of real-world samples of metals, the proposed approach verifies predictions of bidirectional reflectance distribution function (BRDF) models. It employs ellipsometry to verify both the actual polarizing effect and the overall reflectance behavior of the metallic surfaces.
Ellipsometry
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A well understanding of topography effect on the forest reflectance is critical for biophysical parameters retrieval over rugged area. In this paper, a new hybrid bidirectional reflectance distribution function (BRDF) model coupled the geometric optical mutual shadowing (GOMS) and scattering from arbitrarily inclined leaves (SAIL) models with topography consideration (GOSAILT) for sloping forest was proposed.
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Commonly used methods of developing paints and evaluating their performance involve calculating the signatures of vehicles and backgrounds, this requires experimental determination of the directional and bidirectional reflectance of the surfaces involved. This paper describes the measurements required, the instruments used to make such measurements, and computer codes and techniques used for paint development and signature evaluation. Examples of bidirectional reflectance data obtained using full experimental mapping are presented. Applications of BRDF data in IR paint development are demonstrated with emphasis on validation and confirmation of computer modeling codes. Calculations of signatures using BRDF data are given using bidirectional reflectance data for two different coatings.
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Signature prediction models have become an increasingly important tool for the ground combat vehicle designer in recent years. System designers have been successful in prototyping entire vehicles in each spectral band. With this success, focused efforts to improve the accuracy of these signature models have produced robust, validated performance for many operational conditions. One of the most recent improvement in prediction models for ground vehicle systems has been improvements in surface reflectance. Surface reflectance is central to the predicted performance of these models and range from simple to very complex. Simple surface reflectance models treats the surface as totally lambertiant has an advantage of being fast to calculate but does not take into account the specular nature which all surfaces posses. The bi-directional reflectance distribution function (BRDF) is a more complex representation which allows for a more accurate representation of surface reflectance phenomena. The input to the BRDF usually comes from a laboratory sample measured in a laboratory setting. These laboratory samples are made to be perfect so that comparisons can be made between variations in formulas for the coatings. The limitation of these inputs is that surfaces that are exposed to environments effects and normal daily use are the more representative of data we are interested in. Other effects such as the conditions under which the surface coatings are applied can cause reflectance variability as well. This paper explores the variability on real targets and compares them to laboratory samples. The implication of these variations to signature models will be explored.
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ç®æ åååå°åå¸å½æ°BRDFï¼Bidirectional Reflectance Distribution Functionï¼ä¸ä» æ¯éé¢é¥æçå ³é®å°çç©çåæ°ï¼ä¹æ¯æè½½å å¦é¥æ仪å¨åºäºå°é¢ç®æ çåºå°è¾å°æ ¡æ£éè¦åéï¼æ¯å½±åå®æ 精度çå ³é®è¦ç´ ãä¼ ç»éå¤å°ç©å¤è§åº¦æµé使ç¨çè§æµè®¾å¤ï¼ä¸è¬å ¶ç»æè¾ä¸ºå¤æï¼ééä½ç§¯è¾å¤§ï¼èä¸è¿è¾åç»è£ è¿ç¨ç¹çï¼è§æµç®æ æ¶å®¹æåå°å½¢å交ééå¶ï¼é¾ä»¥è¿è¡é«æå¿«é精确çéå¤æµéãè¿å¹´æ¥ï¼æ 人æºç±äºå ¶è®¾å¤æä½ç®ä¾¿ãè¿è¾åè§æµæ¹å¼çµæ´»çæ¹é¢çä¼ç¹ï¼å¯ä½ä¸ºæ°çè§æµå¹³å°åºç¨äºå½åé¥æè¯éªä¸ãæ¬æ设计äºä¸ç§åºäºæ 人æºå¹³å°çå°è¡¨BRDFæµéè£ ç½®ãè§æµæ¹æ¡åæ°æ®å¤çæµç¨ãå©ç¨å¤æ翼ä½ç©ºæ 人æºåäºå°çç»åï¼æè½½éå¤å°ç©å 谱仪åè·æç¸æºï¼éè¿å¯¹å°é¢ç®æ å¤è§åº¦è§æµåé«ç²¾åº¦å®ä½åè§åº¦æ§å¶ï¼å®ç°é对åºå®ç®æ çå¤æ¹ä½è§å天顶è§è§æµãæ¬æéç¨ä¸è¿°è®¾è®¡æ¹æ¡åè§æµæµç¨ï¼å¨æ¦ç è¾å°æ ¡æ£åºå¼å±å¤æ¬¡ç¨³å®ååæ²æ¼ ç®æ çå¤è§åº¦å è°±è§æµè¯éªï¼å¹¶å©ç¨å®éªè§æµæ°æ®ï¼åºäºRoss-Liæ ¸é©±å¨æ¨¡åæ¨ç®äºåºå°BRDF模ååæ°ï¼å¹¶ä¸MODISçé表BRDF产åï¼MCD43C1ï¼ååå°ç产åï¼MOD/MYD09ï¼è¿è¡å¯¹æ¯éªè¯ãéè¿å¼å±éå¤å®éªï¼æ ¸éªäºè¿ç§æ°çBRDFè§æµæ段çå¯é æ§ï¼è·åçæ¦ç å°è¡¨BRDFåæ°ä¸MODISé¥æ产åæè¯å¥½çä¸è´æ§ï¼å波段çç¸å¯¹åå·®å¨5%以å ãæ¬ç 究表æï¼åºäºå¤æ翼æ 人æºçBRDFè§æµç³»ç»ï¼æä¾äºä¸ç§å ¨æ°çå°ç©ç®æ æ¹ååå°ç¹æ§è§æµæ¹æ³ï¼å¯ç¨äºèªå¨åé«é¢æ¬¡åºå°ç¹æ§è§æµä»¥åå«æåæ¥å®æ çéå¤å®éªæ´»å¨ãå¨ä¿è¯è§æµç²¾åº¦çåæ¶ï¼æ大å°å轻人åç©åçæå ¥ï¼å¼å¾å¹¿æ³æ¨å¹¿åºç¨ã
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Scene simulation has proved to be a valuable tool for analysing the images perceived by visible and infrared imaging systems. Accurate scene simulation requires accurate incorporation of the optical properties of all the materials within a scene, with reflectance incorporated with the bidirectional reflectance distribution function (BRDF) and emission incorporated through the directional emissivity or hemispherical directional reflectance (HDR). This paper compares the fit of various parameterised models to experimental BRDF data from a variety of surfaces representing the extremes of material properties found in the environment. One of the main aims is to infer the accuracy and validity of an in-house BRDF model called Mopaf using data representative of different sorts of isotropically reflecting materials. Where appropriate physical and semiempirical models and a novel parameter based BRDF model were compared with Mopaf and with BRDF data from a Surface Optics Corporation SOC-200 instrument. It was concluded that Mopaf might not be reliable for all the angular BRDF data, especially specularly reflecting surfaces or grazing incidence data. Likewise, the other BRDF models investigated tended to be limited to a range of physical conditions such as only diffuse reflection or to a range of surface roughness. It was shown that the proposed new BRDF model was more generally applicable from the visible to infrared wavelengths, over a wide range of reflection angles and for different sorts of surface material.
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Two characteristics are critical in the understanding of target signatures, physical surface temperature and surface reflectance. An objects surface reflectance can be thought of as having two major components, the diffuse and specular components. The best way to understand these components is by examining the Bi-directional Reflectance Distribution Function (BRDF). The BRDF provides an understanding of the reflectance behavior of a surface from every incident angle and reflectance angle. With the BRDF one can provide an accurate computer model of how the material behaves. Databases of BRDF data are available for use in modeling and simulation of targets but are typically comprised of pristine samples that may not be representative of real world targets. This paper will provide methods, data and trends of the BRDF variability in the infrared regions. We will also explore appropriate data sets for use to represent typical fielded targets.
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Scene simulations of optical signature properties using signature codes normally requires input of various parameterized measurement data of surfaces and coatings in order to achieve realistic scene object features. Some of the most important parameters are used in the model of the Bidirectional Reflectance Distribution Function (BRDF) and are normally determined by surface reflectance and scattering measurements. Reflectance measurements of the spectral Directional Hemispherical Reflectance (DHR) at various incident angles can normally be performed in most spectroscopy labs, while measuring the BRDF is more complicated or may not be available at all in many optical labs. We will present a method in order to achieve the necessary BRDF data directly from DHR measurements for modeling software using the Sandford-Robertson BRDF model. The accuracy of the method is tested by modeling a test surface by comparing results from using estimated and measured BRDF data as input to the model. These results show that using this method gives no significant loss in modeling accuracy.
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