工程光学英语补充内容和习题.ppt

2. Two lenses, a lens of 12.5cm focal length and a minus lens of unknown power, are mounted coaxially and 8 cm apart. The system is afocal, that is light entering the system parallel at one side emerges parallel at the other. If a stop 15mm in diameter is placed halfway between the lenses: 1) Where is the entrance pupil? 2) Where is the exit pupil? 3) What are their diameters? Homework Keywords and concept 1. Aberrations Monochromatic aberrations (Spherical aberration, coma, astigmatism, curvature of field, distortion) Chromatic aberrations Keywords and concept 2. Monochromatic aberrations can be further divided into two groups depending on whether or not they cause the image blur. Image blur occurs in spherical aberration, coma and oblique astigmatism. Keywords and concept Curvature of field and distortion cause dislocations within the image but no blur. 3. Wave aberration: The degree of departure from true sphericity,that is, the distance between the ideal reference sphere and the actual, distorted wavefront, measured along the radius of the reference sphere. Keywords and concept Homework Answer the following questions: 1. What is an aberration? How does it come? 2. How can we classify the aberration? 3. What is wave aberration? What relationship among wave aberration and other aberrations? Homework Reading the complementary information and fill in the following form: Homework Answer 1. What is an aberration? How does it come? An aberration is the difference between the real image and the ideal image. In paraxial-ray tracing, which we discussed earlier in conjunction with single surfaces and thin lenses, we had assumed that the angles which the rays subtend with the optic axis are small. If this is so, the sines of these angles can be set equal to the angles themselves( in radians). In fact, the angles are larger, and if we use exact ray tracing, this can no longer be done. The sine of an angle must then be represented by a series expansion. So the