圖像色彩的分光研究

Abstract

「色彩」在我們的生活中隨處可見，用來描述色彩的方法，可分為兩大表色系統，一為顯色系統，以色彩三屬性--色相、彩度與明度來描述；另一為混色系統，以三原色R、G、B來表示，而顯色系統的表示法最貼近生活中對色彩的感覺。從實地觀測物體的反射光譜，以量化的方式了解色彩的物理本質。這項研究工作的成果在於： 1.認識色彩三屬性的物理內涵： 根據圖像的分光反射率，建立主波長的操作型意義，因而可以定量地表示色相。彩度可根據主波長分光反射率平均值與分光反射率極小值的差來衡量。明度決定於物體反射光總強度，且實際色光總強度可由RGB三個數值的總和而得知。 2.了解混合色光的光色與單色光成分的關係： 根據兩單色光以不同強度比例混合的實驗，可產生成分波長以外的光色。建立成份光強度與光色關係的基本資料，可作為利用光色來推測原始成分光強度的參考。 3.分析顯示幕圖案的光色 顯示幕所呈現的顏色屬於加法混色，雖然CRT與LCD兩種顯示幕的三原色的光譜形式不相同，但經由不同比例的混光後，可得到相同的色彩表現。這個結論與前一項成果一致。 4.推算單狹縫繞射圖案的色彩分布： 中央亮紋與普通亮紋的寬度可以用RGB的總和來判讀。若以日光當入射光源，可以用主波長的概念來判讀，單狹縫繞射第一彩色條紋所呈現的光色為黃色。由分光反射率平均值與極小值的差，可得其彩度的高低。對於其他類型混合光，亦可推算其圖案色彩分布方式。

Color can be seen everywhere. There are two main color specification systems. One is color appearance system, which describes color by its three quantities-- hue, saturation, and brightness. The other is color-mixed system, which divides color into trichromacy (red, green, and blue). We usually use color appearance system to describe color in our daily life. We measure reflecting spectrum of objects to find out the character of physics on color. Conclusions we made show below: 1.Understanding physical meaning of three quantities of color. According to reflectional spectrum of pictures, we can measure hue by main wave length. Saturation can be measured by the difference of the average of spectral reflectance of the main wave length and the minimum of spectral reflectance. Brightness is determined by the intensity of reflectance of objects. Therefore, the total intensity of reflectance of objects can be gotten by the sum of RGB values. 2.Relationship between color of mixing lights and monochromatic light After two monochromatic light are mixed in different proportion of color intensity, they can produce another color which is beyond wave length of components. It makes relation between intensity of component lights and color. Then we can infer intensity of original component lights from color of lights. 3.Analysis of colorful pictures in monitors. Color from monitors belongs to RGB additive primaries. Although different spectral forms of trichromacy in CRT and LCD, we still can get the same color by different proportion of mixing colors. The third conclusion is the same as the second conclusion. 4.Guess the color distribution of single-slit diffraction pictures. We can get the width of central bright stripe and ordinary bright stripe by the sum of RGB. In addition, we use concepts of main wave length to make a conclusion. Take the sun light as an example, yellow is the color of the first colorful stripe in single-slit diffraction. Saturation can be measured by the difference of the average of spectral reflecatance of the main wave length and the minimum of spectral reflectance. We can also guess the color distribution of pictures in other forms of complex lights.