Out-of-field rejection filters for optical systems
AssigneeNorthrop Grumman Systems Corporation
InventorKevin J. Romero
Life of this patent
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Abstract
An out-of-field rejection filter (OFRF) can be used in optical systems to reject stray light. Such optical systems can include cameras, projectors, star trackers, and virtual reality or augmented reality displays. The OFRF can include a converter to convert randomly polarized light to p-polarized light and an angular selectivity layer to select in-field p-polarized light and reject out-of-field p-polarized light. The converter and the angular selectivity layer are configured so as to filter out-of-field light while passing in-field light within a light bandwidth. The angular selectivity layer can be a multilayer film of interleaved materials having alternating permittivity and magnetic permeability properties.
Claims20
An out-of-field rejection filter comprising:
- a converter configured to convert randomly polarized light to p-polarized light;
- and
- an angular selectivity layer configured to select in-field p-polarized light and reject out-of-field p-polarized light, the angular selectivity layer being a multilayer film comprising tens or hundreds of interleaved layers of alternately different materials arranged to achieve tuned angular selectivity, the individual interleaved layers of the angular selectivity layer being alternately composed of materials with high and low indices of refraction nhigh and nlow, the indices of refraction of at least some of the individual interleaved layers of the angular selectivity layer conforming to the relationships nhigh=√(εhigh/ε0)=√(2εlow/ε0) and nlow=√(εlow/ε0)=√(εhigh/ε0)/√2,
- the converter and the angular selectivity layer being configured so as to filter out-of-field light while passing in-field light within a light bandwidth.
An optical system comprising:
- an afocal fore-optic comprising one or more refractive or reflective optical elements configured to input and output a collimated field, the light rays of the collimated field having any polarization;
- an out-of-field rejection filter comprising:
- a polarization converter configured to convert randomly polarized light to p-polarized light;
- and
- an angular selectivity layer configured to select p-polarized light and reject out-of-field polarized light;
- an aft-optic comprising one or more refractive or reflective optical elements configured to either create an image on a focal plane or to provide a collimated exit pupil.
An out-of-field rejection filter comprising:
- a converter configured to convert randomly polarized light to p-polarized light;
- and
- an angular selectivity layer configured to select in-field p-polarized light and reject out-of-field p-polarized light, the angular selectivity layer being a multilayer film comprising tens or hundreds of interleaved layers of alternately different materials arranged to achieve tuned angular selectivity, the individual interleaved layers of the angular selectivity layer being alternately composed of materials with high and low indices of refraction nhigh and nlow, at least some of the individual interleaved layers of the multilayer OFRF angular selectivity layer alternately comprising lithium fluoride and zinc sulfide,
- the converter and the angular selectivity layer being configured so as to filter out-of-field light while passing in-field light within a light bandwidth.
An out-of-field rejection filter comprising:
- a converter configured to convert randomly polarized light to p-polarized light;
- and
- an angular selectivity layer configured to select in-field p-polarized light and reject out-of-field p-polarized light, the angular selectivity layer being a multilayer film comprising tens or hundreds of interleaved layers of alternately different materials arranged to achieve tuned angular selectivity, the individual interleaved layers of the angular selectivity layer being alternately composed of materials with high and low indices of refraction nhigh and nlow, the out magnetic permeability of at least some of the high-index-of-refraction layers of the multilayer OFRF angular selectivity layer having a magnetic permeability μhigh that is twice the magnetic permeability of at least some of the low-index-of-refraction layers of the multilayer OFRF angular selectivity layer material,
- the converter and the angular selectivity layer being configured so as to filter out-of-field light while passing in-field light within a light bandwidth.
Dependencies are inferred from the claim text.