Subtractive method of optical thin-film interference filter design.

A fast automatic synthesis program based on interference minus filters is described. It yields the parameters of a number of individual filters that together match any desired spectral transmittance curve, providing that the spectral range over which the latter is defined is not excessive. It is shown that in practice many of these components can be combined without significantly affecting the performance. When used alone, the program may yield solutions consisting of a large number of layers. It is demonstrated that far fewer layers are needed if intermediate solutions obtained with this program are refined using other automatic synthesis programs. The program is illustrated by a number of rather difficult hypothetical problems.