t31

说明：  偶数波带片：将波带片所在屏幕分为1001*1001个点，依次求出各点处的半波带数，为奇数则涂黑，为偶数则不涂黑表示透光。设波带片中心为原点。
(Even waveband plate: divide the screen where the waveband plate is located into 1001 * 1001 points, and find out the number of half waveband at each point in turn. If it is odd, it will be blackened, if it is even, it will not be blackened, indicating light transmission. Let the center of the zone plate be the origin.)