Multiple effective focal length (EFL) optical system

A compound lens optical system, comprising:

• a series of lenses having a Gaussian lens arrangement configured to transmit light having a first wavelength and/or polarization and light having a second wavelength and/or polarization;
• and
• a plurality of mirrors arranged within the Gaussian lens arrangement and comprising:
• a first mirror, comprising a dichroic or polarizing mirror coating or patterned optical surface and configured to transmit light having the first wavelength and/or polarization and to reflect light having the second wavelength and/or polarization;
• and
• a second mirror, comprising a dichroic or polarizing mirror coating or patterned optical surface, having an annular shape and configured to transmit light having the first wavelength and/or polarization and to reflect light having the second wavelength and/or polarization,
• wherein the Gaussian lens arrangement is configured to focus light having the first wavelength and/or polarization at a first focal plane having a first back-focal distance, and
• wherein the plurality of mirrors are configured to focus light having the second wavelength and/or polarization at a second focal plane having a second back-focal distance that is different from the first back-focal distance.