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透明表面上的入射光可以根据光学定律反映，传输或吸收。
每当两个不同的表面之间存在边界时，光就会折射，因为当光速从一种材料到另一种材料时，光速会发生变化。它弯曲的方向，即朝着正常入射线的沿或远离正常入射线的方向取决于速度在越过边界时降低还是增加。亚博网站下载折射率最高的材料最大的降低了光波，因此弯曲最高。
透明的材料使光线可以通过亚博网站下载，而无需任何入射光吸收。但是，半透明的材料不会传输大多数通过它们的亚博网站下载光线，因为它们具有导致光散射的结构。
Translucent Materials
斯内尔的定律指出，在通过边界通过边界时，发射率和光的折射的罪过的比率保持恒定，用于确定当光从一种介质到另一种介质传递到另一种介质时的光线如何表现。半透明的材料使光线通过，亚博网站下载但不一定遵循斯内尔定律。
在这些材料中，光子亚博网站下载可以散布在折射率发生变化的任何接口上，并且可能会有内部反射，从而使一部分光入射被吸收，传输和反射。
传输可以直接穿过，扩散或两者之间的东西。在测量半透明材料的传输时，漫射材料和非扩散材料之间的这种差异会引起其他挑战。亚博网站下载
传输测量
Transmission measurements usually consist of two steps. First, establishing a spectral baseline by measuring a standard light source without the material, and then, measuring with the sample. The difference between the measurements gives the transmission characteristics of the material.
标准光源作为参考，例如能够发射测试样品的整个波长范围的LED或卤素灯源，例如LED或卤素灯源，并且需要检测到测量值。
If light is not emitted at certain wavelengths, none is transmitted, so no properties can be ascertained from the measured data. Another important point is that the overall spectral sensor response along with the spectral power distribution of the light source should have a suitable signal-to-noise ratio.
If the angle of the transmitted beam through a translucent material can be calculated from the incident angle and Snell’s law, the transmission measurement setup for translucent materials is simple. However, in some materials and applications scattering can be important, particularly in diffusing filters.
半透明要求
When considering the measurement geometry it is important to take into account that translucent materials (diffuse and non-diffuse) have very specific transmission properties. Various options, including using lenses/collimators for emitting and receiving light, cosine correctors, integrating spheres, and combinations of these optics are possible.
如果半透明的材料高度扩散，则可能需要集成球来收集所有光。但是，这可能会由于低光输出而降低信噪比，从而不利地影响测量值。
Light Sources and Spectrometers
A light source and detector that match the desired spectral region of the material of interest are important for obtaining good spectral data. A range of Steropes light sources are available from Admesy including white and colored LED light sources and halogen with optional blue enhancement filter. These light sources cover a broad spectrum from visible to near infrared and are suitable for a majority of applications.
An important part of obtaining useful transmission measurement data is the spectrometer configuration. Along with being sensitive over the wavelength range of interest, suitable optical resolution for the application is also necessary.
来自Admesy的Rhea系列光谱仪
由于冷却的Hamamatsu CCD检测器，Admesy的RheA系列光谱仪在200至1100 nm之间完全可定制和敏感。Rhea的特征是：
- 可用于从10–100 µm的缝隙尺寸（控制进入光学台的光量）。较小的缝隙尺寸减少了FWHM并增加了分辨率
- Gratings sizes range from 200 to 1800 grooves/mm. A spectrometer grating disperses light into individual wavelengths and dispersion is determined by the number of grooves, given by grooves/mm. The higher the number of grooves, the higher the dispersion.
- 可自定义的光栅可以在RHEA上使用，从而可以分析宽或特定的波长范围。尽管较高数量的凹槽增加了分散体，但由于检测器具有固定宽度，这也限制了可以解决的波长范围。
- RHEA包括具有快门功能和5 nd滤波器的过滤轮（OD0作为标准位置，OD1，OD2，OD3和OD4）。这使光谱仪具有较大的动态范围并测量高于4.0的光密度。
- 可以确定开始和末端波长，以使用光栅选择和对齐方式拟合特定的传输测量应用。
一个完全可定制的设置和宽的动态范围，允许超过200-1100 nm的传输测量值，使RHEA成为透明材料中光谱测量的理想光谱仪。亚博网站下载仪器中的光栅数量正在增加，这将增加RHEA的配置数量，从而扩大其有用性。
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参考
- Fox, M., 2002, Optical Properties of Solids. Oxford University Press.
- 申请注，传输测量，Rhea和Steropes，Admesy，2017年
- Yamashita，我。等，2008，透明陶瓷，J。Am。陶瓷。Soc。91（3）：813。
- Singh，S.，2009年，《光学工程基础》，发现出版社。
This information has been sourced, reviewed and adapted from materials provided by Admesy.
有关此消息来源的更多信息，请访问Admesy。