数码镜头设计原理.ppt
34页
数码镜头设计原理 分辨率分辨率Click to add TitleClick to add TitleClick to add TitleClick to add Title ContentsClick to add Title1Click to add Title2Click to add Title3Click to add Title4 数码镜头的分辨率（鉴别率）数码镜头的分辨率（鉴别率）数码相机鉴别率定义为在象面处镜头在单位毫米上可鉴别的黑白线对数数码相机鉴别率定义为在象面处镜头在单位毫米上可鉴别的黑白线对数 两黑线中心距（两黑线中心距（2d2d）＝）＝1/1/鉴别率（线对鉴别率（线对/ /毫米）毫米）两个主要用途两个主要用途1 1、根据镜头对分辨率的要求，计算出检校分划板的要求、根据镜头对分辨率的要求，计算出检校分划板的要求2 2、根据接收元件的象元特点确定镜头的分辨率要求、根据接收元件的象元特点确定镜头的分辨率要求 CCD的分辨率的分辨率CCDCCD的分辩率是用象素总数表示的的分辩率是用象素总数表示的设在水平方向上设在水平方向上CCDCCD感光有效长度是感光有效长度是M M毫米，在垂直方向上有效长度是毫米，在垂直方向上有效长度是N N毫米。
毫米如果象素（最小感光单元称之为象素）的尺寸是如果象素（最小感光单元称之为象素）的尺寸是m2 * n2m2 * n2，，那么在水平方向上的象素总数那么在水平方向上的象素总数=M/m2=M/m2，在垂直方向上的象素总数，在垂直方向上的象素总数=N/n2 =N/n2 数码镜头分辩率与数码镜头分辩率与CCDCCD分辩力的匹配分辩力的匹配 在水平方向上数码镜头对线状分辩率图案的成象，其每个线宽恰好站用在水平方向上数码镜头对线状分辩率图案的成象，其每个线宽恰好站用一个象素，我们就称在水平方向上选用的一个象素，我们就称在水平方向上选用的CCDCCD与数码镜头在分辩率上是相与数码镜头在分辩率上是相配的配的 ，垂直方向同理这样定义保正了，垂直方向同理这样定义保正了CCDCCD在最少象素总数下，恰好能在最少象素总数下，恰好能分辩清象的细节分辩清象的细节 即：即：一个线宽对应一个象素一个线宽对应一个象素设CCD的M=1mm，N=1mm镜头象方分辩力=15线对/毫米，现计算其象素总数如下：由（1）式有：d=1/(2*镜头象方分辩力)=1/30=0.03333(毫米/每黑白线对)可见与该镜头相配的CCD最小感光单元象素尺寸m2*n2=0.03333*0.03333毫米由（2）式有：CCD象素总数=1/(0.03333)*1/(0.03333)=900象素如果镜头鉴别率是150线对/毫米，CCD感光面M=4.8mm，N=3.6mm。
由（1）式有：d=1/(2*镜头象方分辩力)=1/300=0.003333(毫米/每黑白线对)由（2）式有：CCD象素总数=4.8/(0.003333)*3.6/(0.003333)= 1920000象素这就是说分辩率是150线对/毫米的镜头，可配1/3英寸200万象素的CCD CCD感光面尺寸感光面尺寸1英寸3/4英寸 1/2英寸 1/3英寸 1/4英寸CCD尺寸12.8*9.68.8*6.66.4*4.84.8*3.63.6*2.7对角线尺寸 1611864.5常用CCD MTF域值＝0.15常用CCD 饱和照度＝100LX常用CCD 域值照度＝0.02～0.5LX CCD上镜头分区域鉴别率要求上镜头分区域鉴别率要求•在CCD上0.7视场的MTF=0.3时的频率定为该镜头的鉴别率 •同时要求0.7视场内的鉴别率都要比它高中心视场鉴别率至少应是它的1.5倍 •考率象面分辩率整体性，边缘视场最好不低于0.7视场的0.3倍 CCD上不同分辨率下上不同分辨率下MTF要求要求•镜头的低频分辩率决定了物体象轮廓的清析度•镜头的中频分辩率决定了物体象的层次感（即在一定物空间内都较清楚）•镜头的高频分辩率决定了分遍物体象细节的能力 •好的MTF曲线应接近一条倾斜的直线。
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