这是第一篇科研日志_18.09.19_09.20_Keep going

思考的几个问题
1、固有光学参数的反演实验设计
2、水体漂浮微塑料的光谱特性测定

学习了几个问题

1、Labsphere Spectralon plaque

最初误解，与积分球区别

Integrating spheres collect reflected light from samples over a full hemisphere. The sphere, by nature of its internal diffuse (lambertian) reflection and integration of the energy, is insensitive to directional reflectance features coming from the sample, and therefore, gives a very repeatable “averaged” response to the reflectance of the sample placed in the beam at the sphere port. Sample placement and incidence beam/collection alignment are less critical to the measurement results because the integrating sphere looks at representative averaged energy from all angles at the same time.

蓝菲光学SPECTRALON®漫反射标准板
Spectralon TM, a commercially available diffuse reflectance material made from polytetrafluoroethylene (PTFE), has been baselined in the MISR design.

In the realm of optical spectroscopy, it is essential that calibration targets and reflectance standards remain as stable and constant as possible,andreproducibility is vital. Labsphere Inc. produces a sintered polytetrafluoroethylene (PTFE) reflectance standardknown as Spectralon [1]. It is chemically in-ert, and thermally and environmentally stable,provid-ing extremely stable, reproducible spectral reflectance close to 99% from 350 -2500 nm [2]. Labsphere has been ableto create diffuse reflectance standards that can offer the highest diffuse reflectance values of any known substance [3].

[1] Helmlinger M. and Arecchi A. (2012) CalCon.
[2] labsphere.com/news/labspheres-space-grade-spectralon-conquers-final-frontier/
[3] lab-sphere.com/products/reflectance-reference-standards-targets/reflectance-standards/calibrated-diffuse-reflectance-standards-set/

from：Temporal Variations in Spectral Reflectance of Spectralon（2016）

2、为何要用75%的蓝菲参考板而不是99%的参考板？50%灰度板的作用(使用方法）？

• 对于朗伯面/体来说，辐照度E是辐亮度L的半球积分。
• “理想的漫反射源单位表面积向空间指定方向单位立体角内发射/反射的辐射功率和该指定方向与表面法线夹角的余弦成正比”——朗伯余弦定律。``

Gray scale Spectralon is used to establish the linearity and accuracy of reflectance spectrophotometers and colorimeters, much in the way that calibrated neutral density filters are used in transmittance instruments. While standard Spectralon gray scale sets are suitable for users who need a wide dynamic range of reflectance, certain applications require sets of gray scale that are abbreviated in range but not in the number of steps of calibration. Industries such as clay and processed minerals, paper and paints may require such a scale, which fairly accurately reproduces the range of reflectances shown by such products.

3、reflectance 和 albedo 的区别

• Reflectance翻译为“反射率”，是用来衡量物质反射能力的量，定义为物体表面反射能量与到达物体表面入射能量的比率。反射率是波长的函数，且一般为正。
• Albedo翻译为“反照率”，是指目标物的出射能量与入射能量之比值，或称半球反射率。它是反演很多地表参数的重要变量，反映了地表对太阳辐射的吸收能力。反照率又分为白空反照率（White Sky Albedo, WSA）和黑空反照率（Black Sky Albedo,BSA）。所谓BSA是指忽略大气散射，只考虑地物对太阳直射入射辐射的反射情况；而WSA则是忽略太阳直射辐射只考虑地物对大气散射辐射的反射情况。地物真实反照率又被称为蓝空反照率（Blue Sky Albedo），又称半球-半球反射率（BHR）其计算公式为：BHR ≈ （1- s）WSA + sBSA,其中S为天空散射光比例。
• 反射率（reflectance)：物体表面所能反射的能量和它所接受的能量之比；是指某一波谱段向一定方向的反射。
• 反照率（ albedo ）：反照率(Albedo)又称半球反射率，定义为目标地物的反射出射度与入射度之比，即单位时间、单位面积上各方向出射的总辐射能量与入射的总辐射能量之比；是反射率在所有方向上的积分；
• 区别：反射率是波长的函数，不同波长反射率不一样，反照率是对全波长而言的。
• 1.reflectance是指某一波段向一定方向的反射，albedo是反射率在所有方向上的积分。
• 2.reflectance是波长的函数，不同波长reflectance不一样；albedo是对全波长而言的。

明天要弄明白的问题
1、双向反射率分布函数BRDF

需要记住的几个tips
1、面对不理解的问题 尝试去弄明白 并用自己的语言来记录。切忌一知半解
2、没弄明白的问题不要轻易张嘴
3、做科研不能急功近利

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