L16-C5-4 典型系统的光束选择(II).ppt

1、应用光学Applied Optics,光信息0801-02 2010-2011第一学期,2,第五章 成像光束选择,3,C5-5. 典型系统的光束选择 （II）,4,典型光学系统光束选择,5,三、显微镜,结构与望远镜类似，但为有焦系统 物镜的像位于目镜的物方焦平面上，系统出射光线为 平行光线 视放大率= 250/f(mm)=oe,6,显微镜,孔径光阑- 物镜框 视场光阑- 目镜物方焦面上的光阑或分划板,一、观察显微镜,7,显微镜,线视场,一般，视场光阑的直径大约为20mm，故线视场 2ymax=20/o,8,物方孔径角u、数值孔径NA=nu,显微镜,物镜的物方和像方孔径角为u、 u 因为物镜为孔

2、阑，故u也为显微镜的物方孔径角,若显微镜出射口径为D，则,思考：高倍显微镜中通常会使用浸液物镜，为什么？,9,To ensure the diameter of emergent rays , we can get D1mm thus, NA/500,Methods of increasing NA: NA=nu 1. To enlarge u; 2. To Increase n. We can immerse the objective into liquid with high index, such as oil .,NA is always wanted to be larger. 1

3、.NA= D /500. Suppose D is constant，if we want to increase , we need to enhance NA. Suppose is constant , if we want to increase D, we also need to enhance NA.,2.NA is related with the resolution of a microscope. The larger the NA is, the higher the resolution is.,显微镜,10,For example, if a microscope

4、adopts an eyepiece with the magnifying power of 15x, and an objective with the lateral magnification of 3x, then the magnifying power of the microscope will be:,Generally the NA of a 3x objective lens is 0.1, and the eyepieces with 5X,6X,10X,15X, can all match with the objective with NA=0.1.,显微镜,11,

5、例： 200倍显微镜的目镜焦距为25mm，求显微镜的线视场；若出瞳直径为1mm，物像共轭距为195mm，求显微镜的数值孔径；物镜的通过孔径多少（均按薄透镜计算）？,显微镜,12,1) The microscope which can measure the height of objects:,2y,2y,As the distance between the objective and the reticule is fixed, the corresponding is then a constant . we can get the height y of object by measu

6、ring the height of image y. y=y/,The object plane must be positioned precisely in order to make the image plane fall just on the reticule, or else, there will be some errors.,二、测量显微镜,显微镜,13,A1,B1,A,B,B,A ,B1,A1,y1,y,If the object plane is not positioned precisely ,The cause of errors:,What we measur

7、e now is the distance between the centers of the two blur spots, and the centers is the intersections of the chief ray and image plane. As the aperture stop is still on the frame of the objective, the chief rays will change along with the movement of object plane, then the intersections will also ch

8、ange.,Way of solving this problem: Making the position of chief rays fixed,显微镜,14,Aperture stop,y1=y,The incident chief rays are always parallel to the axis, and the emerge chief rays will not change, and the intersection of it on the image plane will also not change.,Object telecentric(焦阑) system :

9、 Put the aperture stop on the second focal plane, and the entrance pupil is located at infinity.,孔径光阑- 物镜像方焦平面上安装的光阑 视场光阑- 目镜物方焦面上的光阑或分划板,显微镜,15,2) The microscope used in geodetic instrument or projector（大地测量仪或投影仪中）,FO,y,y,fO,-l,We need measure the distance l, given the focal length of objective f a

10、nd the height of object y, after measuring the height of image y, we can get the object distance l,If the aperture stop is on the frame of the objective and if there is a slight defocusing, the errors will be introduced.,显微镜,16,y,y1,When the image plane does not fall on the reticule:,显微镜,17,The chie

11、f ray of the emergent rays will be always parallel to the axis, and the intersection of it on the image plane will also not change.,Image telecentric system: The aperture stop is located at the first focal plane of the objective, and the exit pupil is located at infinity.,显微镜,18,小结 视场光阑 - 目镜物方焦面上的光阑

12、或分划板 孔径光阑 - 如下,显微镜,思考 孔径光阑的选择，在两种用途下为何不同？,19,例： 若上例中的显微镜用于测量，问物镜的通光口径需要多大？孔径光阑需要多大？,显微镜,20,5.7 Properties and Applications of Field Lens 场镜,1. Functions of field lens,21,定义： 与像平面重合，或很靠近像平面的透镜，称为场镜 作用： 在不影响系统成像性质（D/f, 2w, f等）的情况下，改变成像光束的位置,应用： 1. 望远系统中，在物镜像平面上加场镜，可以改变出瞳的位置：减小出瞳距离，加正场镜（如图），反之，加负场镜； 2. 某些连续成像的组合系统中，在中间实像平面处加入正场镜，可以减小后面光组的直径； 3. 一些红外系统中，用于减小红外探测器的尺寸; ,22,3. Calculation of the effective focal length of the field lens,确定场镜焦距的方法：根据某一条光线通过场镜前后所要求的位置，用成像关系公式或组合系统的光路计算公式计算。 关键在于：如何找到这条光线？,23,例：有一红外望远物镜，通过口径为25mm，焦距100mm，视场2w=6,问: 1) 不加场镜时，应选多大尺寸的探测器？ 2）若探测器的光敏面为3mm,需要在物镜