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# 电子代写|光纤代写Optical Fiber代考|ELE250 PHOTOMETRY

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## 电子代写|光纤代写Optical Fiber代考|PHOTOMETRY

In photometry, the light is measured in such a way that the measurement result is in accordance with the human vision. A large number of devices are aimed for human use such as computer displays, TVs, and traffic signal lights, therefore they must be tested and evaluated based on the spectral responsivity of the average human eye. Radiometry covers all optical spectral regions, ranging from ultraviolet to infrared, while the photometry only the range of light that is visible for average human eye, that is, in the spectral range from 380 to $770 \mathrm{~nm}$. In the last times, human eye was used exclusively as an optical detector. To measure the intensity of a test light, the test light source was moved and placed at the varied distances from an eye or a screen and compared with the intensity of a standard light source positioned at a fixed position by a visual observation. The distance of the test light source was set so that both light sources, test and standard, appear equally bright. The estimated intensity of the test light source is calculated as the ratio of the intensity of the standard source and the ratio of the distances squared. Such a measured light intensity was named candle power, or in present terminology luminous intensity. This photometric quantity was the first defined photometric quantity. Since the 1940s the human eye, which was predominantly used as an optical detector, has been replaced by a light-sensitive detector (solid-state detector, photomultiplier tube).

Modern photometry measurements have been performed with the help of photodetectors, thus referring to the physical photometry. Physical photometry characterizes the optical radiation with an optical detector that mimics the spectral response of the human eye, that is, it has incorporated weighted spectral response same as the spectral response of a human eye. According to Table 2.1, the photometric units include the lumen or the luminous flux, the candela or the luminous intensity, the lux or the illuminance, and the candela per square meter or the luminance. Each photometric quantity is the spectrally integrated corresponding radiometric quantities weighted by the human eye spectral response.

## 电子代写|光纤代写Optical Fiber代考|SPECTRAL RESPONSE OF A HUMAN EYE

In 1924, the relative spectral response of the human eye was specified by the Commission Internationale de l’Eclairage (CIE), (the International Commission on Illumination). Such a defined relative spectral response of the human eye was called the spectral luminous efficiency for photopic vision with a joined symbol $V(\lambda)$. The relative spectral response is defined in the spectral domain ranging from 360 to $830 \mathrm{~nm}$ and it is normalized to its peak value at $555 \mathrm{~nm}$. The values were republished by CIE in 1983 and adopted by Comité International des Poids et Mesures (CIPM) (the International Committee on Weights and Measures) in the same year. Tabular presentation of the spectral luminous efficiency for photopic vision values at $5 \mathrm{~nm}$ increments is presented in Table 2.3. One can notice from the tabular values that outside the spectral range ranging from 380 to $770 \mathrm{~nm}$, the values of the spectral luminous efficiency for photopic vision are smaller than $10^{-4}$ thus negligible for the calculations.

A photometric quantity $X_{\mathrm{v}}$ can be related to the corresponding radiometric spectral quantity $X_\lambda$ in the following way:
$$X_{\mathrm{v}}=K_{\mathrm{m}} \int_{\lambda=360 \mathrm{~mm}}^{\lambda=830 \mathrm{~m}} X_\lambda V(\lambda) \mathrm{d} \lambda,$$
where $K_{\mathrm{m}}$ is the constant that relates photometric and radiometric quantities and it is named the maximum spectral luminous efficiency of radiation for photopic vision. The value of this constant is defined as the spectral luminous efficiency of radiation at the frequency of $540 \times 10^{-12} \mathrm{~Hz}$ (or at the wavelength of $555.016 \mathrm{~nm}$ in the standard air) to be $K_{\mathrm{m}}=683 \mathrm{~lm} / \mathrm{W}$. This value isn’t defined strictly for the wavelength of $555 \mathrm{~nm}$, where the peak value should appear, but for the wavelength that is slightly shifted from the maximum value. The exact maximum value of the constant $K_{\mathrm{m}}$ can be accurately calculated as $683 \mathrm{~lm} / \mathrm{W} \times V(\lambda=555 \mathrm{~nm}) / V(\lambda=555.016$ $\mathrm{nm})=683.002 \mathrm{~lm} / \mathrm{W}$, which can be simply rounded to $683 \mathrm{~lm} / \mathrm{W}$, with the negligible error.

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## 电子代写|光纤代写光纤代考|人眼的光谱响应

1924年，人眼的相对光谱响应由国际照明委员会(CIE)(国际照明委员会)规定。这种被定义的人眼的相对光谱响应称为光视的光谱发光效率，并用一个联合符号$V(\lambda)$表示。相对谱响应定义在360到$830 \mathrm{~nm}$的谱域内，并归一化到$555 \mathrm{~nm}$的峰值。这些数值在1983年由CIE重新发布，同年被Comité国际计量协会(CIPM)(国际度量衡委员会)采用。表2.3显示了在$5 \mathrm{~nm}$增量处的光视值的光谱发光效率。从表格中的值可以看出，在380到$770 \mathrm{~nm}$的光谱范围之外，光位视觉的光谱发光效率值小于$10^{-4}$，因此可以忽略不计。

$$X_{\mathrm{v}}=K_{\mathrm{m}} \int_{\lambda=360 \mathrm{~mm}}^{\lambda=830 \mathrm{~m}} X_\lambda V(\lambda) \mathrm{d} \lambda,$$

## MATLAB代写

MATLAB 是一种用于技术计算的高性能语言。它将计算、可视化和编程集成在一个易于使用的环境中，其中问题和解决方案以熟悉的数学符号表示。典型用途包括：数学和计算算法开发建模、仿真和原型制作数据分析、探索和可视化科学和工程图形应用程序开发，包括图形用户界面构建MATLAB 是一个交互式系统，其基本数据元素是一个不需要维度的数组。这使您可以解决许多技术计算问题，尤其是那些具有矩阵和向量公式的问题，而只需用 C 或 Fortran 等标量非交互式语言编写程序所需的时间的一小部分。MATLAB 名称代表矩阵实验室。MATLAB 最初的编写目的是提供对由 LINPACK 和 EISPACK 项目开发的矩阵软件的轻松访问，这两个项目共同代表了矩阵计算软件的最新技术。MATLAB 经过多年的发展，得到了许多用户的投入。在大学环境中，它是数学、工程和科学入门和高级课程的标准教学工具。在工业领域，MATLAB 是高效研究、开发和分析的首选工具。MATLAB 具有一系列称为工具箱的特定于应用程序的解决方案。对于大多数 MATLAB 用户来说非常重要，工具箱允许您学习应用专业技术。工具箱是 MATLAB 函数（M 文件）的综合集合，可扩展 MATLAB 环境以解决特定类别的问题。可用工具箱的领域包括信号处理、控制系统、神经网络、模糊逻辑、小波、仿真等。