Multiple effective focal length (EFL) optical system
View Patent ↗A multi-band/multi-polarization reflective or catadioptric optical system yields differing effective focal lengths (EFLs) per band/polarization. This approach could be used to create an imaging system, for example. In such case, a sensor (imager, spectrometer, diode, etc.) is located at the one or more focal planes. On the other hand, it could also be used to create a projecting system or hybrid projecting and imaging system by locating an emitter such as an LED, laser, etc.) at the image or focal plane. The system employs polarizers and/or dichroic coatings nano patterns to create different focal lengths and/or fields of view using the same mirrors and/or lenses by, for example, including at least one dichroic coating optically in front of at least one additional mirror to separately reflect the different bands or polarizations.
1 . 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.
2 . The compound lens optical system of claim 1 , wherein the first mirror comprises a first dichroic coating and the second mirror comprises a second dichroic coating.
3 . The compound lens optical system of claim 1 , wherein at least one of the first mirror and the second mirror is located within a lens of the series of lenses.
4 . The compound lens optical system of claim 1 , wherein at least one of the first mirror and the second mirror is located on a surface of a lens of the series of lenses.
5 . The compound lens optical system of claim 1 , wherein the second mirror is closer to the second focal plane than the first mirror is to the second focal plane.
6 . The compound lens optical system of claim 1 , wherein at least two lenses of the series of lenses are between the first mirror and the second mirror.
7 . The compound lens optical system of claim 1 , wherein the first back-focal distance is from a last lens of the series of lenses to the first focal plane and the second back-focal distance is from the last lens of the series of lenses to the second focal plane, the last lens being a closest lens of the series of lenses to the first focal plane and to the second focal plane.
8 . The compound lens optical system of claim 1 , wherein the Gaussian lens arrangement comprises a double Gauss lens arrangement.