《应用光学》课程教学课件 Chapter6 Basics of Radiometry and Photometry(112P).pptVIP

Chapter 6 Basics of Radiometry and Photometry The optical system is the transmission system of radiant energy The energy transfer ability has influence on brightness of the image Radiometry: The study of testing, measuring and calculating the electromagnetic wave Photometry: The study of testing, measuring and calculating the visible light 6.1 Solid Angle and its Applications in Photometry 1.Solid Angle and Its Unit the space angle: solid angle 2.The Calculation of The Solid Angle Assume that the slope angle of a cone is α, let us determine the solid angle of the cone: Draw a sphere with a radius of r, assume to take a girdle corresponding with . Then the breadth of the girdle is ，the radius of the girdle is ，so the length of the girdle is ，and the total area of the girdle is 6.2 Basic Ideas in Radiometry and Their Measurement Units 1.Radiant Flux The total energy a radiator radiates in a unit time---- radiant flux ,and the unit is watt. 2. Radiant Intensity We make a solid angle of in a given direction, the radiant flux in the scope of is , the ratio of and is called radiant intensity in the given direction and is denoted by . The measurement unit of the radiant intensity is watt per sterad (W/sr). It shows the characteristics of a radiator that radiates energy in different directions. 3. Radiant Exitance and Irradiance Take a tiny area of around point A, we assume that the radiant flux emitted from the tiny area is , then the radiant exitance of point A is 4. Irradiance It is the opposite of radiation exitance . It is not the radiant flux emitted from the dS, and it shows the radiant flux a certain surface receives. Irradiance is denoted by . 5. Radiance The radiance is equal to the ratio of radiant intensity that is in the given direction on a tiny area around a certain point on the surface of sphere, and