Thus, they can retain their shape unchanged upon further free-spacepropagation.
这样，当光束继续在自由空间传输时，能保持其形状不变。
2
Using a complex analytical signal representation, the free-spacepropagation properties of ultrashort pulsed Bessel-Gauss beams whose waist width is independent of frequency are studied.
使用复解析信号法研究了束宽与频率无关的超短脉冲贝塞尔·高斯光束在自由空间的传输特性。
3
Freespacepropagation and Fourier transfer system are also analyzed and discussed as particular cases.