光谱学

涵盖光电测量、光谱应用、太阳能电池测试、材料科学等技术文件和基础原理,例如,光的绕射原理、单光仪、氙灯原理、大气质量等。

单光仪原理简介

Monochromator Introduction The term monochrome and its variants come to us from the Greek words mono “single” and chroma “colour”. No light source is truly monochromatic; no light source emits light of a single wavelength, all sources containing contributions from a finite range of wavelengths, termed its spectrum. It is often of interest to decompose a source into its component wavelengths, for the purpose of determining the spectral distribution (UV, visible, infrared e...

光的绕射原理

Theory of diffraction Diffraction describes a variety of processes which obtain when waves, such as light, approaches an obstacle of dimension of the order of their wavelength, and is characterized by the apparent bending of the waves around the object, such as is demonstrated across. What is transmitted in the one case is a sharp image of the aperture, and in the other a diffracted image of the aperture (seen , whereby most of the light is transmitted on axis, but at wider angles,...

绕射光学:绕射阶数、绕射光栅的简介

Diffraction orders As noted above, the grating equation may be satisfied at a given angle by a number of wavelengths of different diffraction orders. ▲Figure 1-9:- Existence of diffraction orders This can lead to problems when attempting to measure light in a given diffraction order, when the detection system is capable of sensing the wavelength in the next diffraction order etc.Order sorting is therefore required, and consists of the filtering of the monochromator input wi...

Czerny-Turner 光路结构单光仪

Czerny-Turner Monochromator The Czerny-Turner configuration, uses a plane diffraction grating. ▲Figure 1-12:- Czerny-Turner configuration In order to control the location of diffracted light, the grating should be illuminated by collimated light. Incident light, diverging from an entrance slit is collimated by a first concave mirror. After diffraction from the grating, light is focused to an exit slit by a second concave mirror. As a function of wavelengt...

使用双单光仪

Double monochromators When using a single monochromator such as that shown in figure 1-9, it is possible that light, entering from the entrance slit, be scattered off the walls and structures constituting the monochromator, reach the exit slit. Therefore, at a given wavelength, , an artificially high signal is measured. This is termed stray light and is of concern where low light level measurements are performed where there exists a significant light component at other wavelengths. ...

单光仪的光谱频宽

Monochromator Bandwidth The monochromator bandwidth, defined in nm, is the range of wavelengths seen by the detector at one time, and is directly linked to the monochromator slits in use. This is an important quantity to take into account, particularly when measuring sources have fine spectral features such as line emission- for example the measurement of a source having two spectral lines one nanometre apart with a system bandwidth of five nanometres, will result in the measurement of a...

氙灯的工作原理

Xe Lamp Light Generation Mechanism Xenon short-arc lamps come in two distinct varieties: pure xenon, which contain only xenon gas; and xenon-mercury, which contain xenon gas and a small amount of mercury metal. In a pure xenon lamp, the majority of the light is generated within a tiny, pinpoint-sized cloud of plasma situated where the electron stream leaves the face of the cathode. The light generation volume is cone-shaped, and the luminous intensity falls off exponentially m...

光的性质

Properties of Light The light that we see everyday is only a fraction of the total energy emitted by the sun incident on the earth. Sunlight is a form of "electromagnetic radiation" and the visible light that we see is a small subset of the electromagnetic spectrum shown at the right.The electromagnetic spectrum describes light as a wave which has a particular wavelength. The description of light as a wave first gained acceptance in the early 1800's when experiments by Thomas Young, Fr...

何谓光子转移曲线 (Photon transfer Curve)?

What is Photon transfer Curve? Linear Signal Model Figure 1-1: a. Physical model of the camera and b. Mathematical model of a single pixel. Figures separated by comma represent the mean and variance of a quantity; unknown model parameters are marked in red. As illustrated in Fig. 1-1, a digital image sensor essentially converts photons hitting the pixel area during the exposure time texpby a sequence of steps finally into a digital number. During the exposure time on ave...

大气质量Air Mass (AM)

大气质量Air Mass (AM) 太阳辐射是接近6000 K的黑体辐射,到达地球大气层表面的辐射能量约为1353 kW/m2。辐射能量会因大气吸收而减弱,经过不同大气层路径,相关的强弱也不同。定义大气层外的太阳光谱为AM0,其中大气质量AM (Air Mass)是用来表示大气层吸收,导致太阳光谱与辐射能量减弱的表征。定义θ角为入射太阳光角度与头顶垂直入射的夹角,则大气质量的计算Air Mass= 1/cos θ。 ▲图一 太阳光谱AM0与AM1.5的定义 AM0:太阳光在大气层外的平均照度,也称为太阳常数。世界气象组织(WMO)于1981年公布的太阳常...

AM1.5G与AM1.5D

AM1.5G与AM1.5D AM为Air Mass大气质量(超连结AM),G为Global代表全空辐射,D为Direct代表太阳光直射。太阳光穿透大气层时,不改变其辐射方向称为直达辐射(Direct),漫射辐射(Diffuse)则是被大气层反射和散射后发生方向改变的太阳辐射。全空辐射(Global irradiance)、直达辐射(Direct irradiance)、漫射辐射(Diffuse irradiance)三者的关系如下: ▲图 全空辐射、直达辐射与漫射辐射的关系。 因此,我们可以理解AM1.5D与AM1.5G的定义如下。 AM1.5D: 太阳光以48.2度夹角,穿过1.5倍大气层厚度”直达”测试平面的直...

AM0、AM1.5G与AM1.5D的太阳光谱与辐射强度

AM0、AM1.5G与AM1.5D的太阳光谱与辐射强度 国际标准ASTM E490定义了标准太阳常数(solar constant) u以及AM0的太阳辐射光谱。这个标准所建立的光谱数据是来自高空飞机、航天器与地球表面的实验测量数据搭配太阳光谱辐照度模型而来。 国际标准ASTM E173提供了AM1.5G与AM1.5D的标准太阳光谱辐照度分布,可以用以评估地表用太阳能组件与材料的模拟或评价。 IEC 60904-3的国际标准定义的AM1.5G的光谱辐照度数据,也常应用于地面光伏(PV)太阳能装置的测量参考。 ASTM E173与IEC 60904-3两者所定义的AM1.5G参考光谱十分接...