The computer routine used in a previous paper [J. Opt. Soc. Am. A <b>13</b>, 523 (1996)] for the concatenation of eikonals is quite slow in certain demanding cases. This problem can be overcome by using the order doubling technique developed for this purpose by Forbes [J. Opt. Soc. Am. <b>72</b>, 1097 (1982); <b>73</b>, 782 (1983)] and Forbes and Andrews [J. Opt. Soc. Am. <b>73</b>, 776 (1983)] more than a dozen years ago. Numerical experiments show that this technique speeds up the calculations by two orders of magnitude or more.
© 1996 Optical Society of America
A. Walther, "Eikonal theory and computer algebra II," J. Opt. Soc. Am. A 13, 1763-1765 (1996)