Dual-band optical systems with a projective athermal chart: design.

We introduce a projective athermal chart that is produced as a view plane of the perspective projection of a three-dimensional space consisting of two chromatic dispersive powers and the mean thermal dispersive power. In addition, we show a design method for dual-band optical systems with this chart and a design example of a three-lens optical system operating in the 3-5- and 8-12-mum wavelength bands.