Systems and methods of sensor calibration using switchable in-path optical diffuser
Systems and methods of calibrating a sensor using an in-path optic capable of remaining in the sensor's optical path of view for both nominal imaging and for solar calibration collects are described. The optic is reversibly switchable between a transparent state and a diffuse state. An electric field aligns a plurality of liquid crystals dispersed in a polymer between two conductive layers is created to enable the transparent state. Incident light is transmitted through the aligned liquid crystals. The electric field between the two conductive layers is removed, misaligning the plurality of liquid crystals dispersed in the polymer between the two conductive layers. Light dispersed by the misaligned liquid crystals is received, and the sensor is calibrated based on the light dispersed by the misaligned liquid crystals.
1 . An imaging system, comprising:
a focal plane-array detector;
one or more of a lens and a mirror;
a plurality of liquid crystals dispersed in a polymer between first and second conductive layers;
a first fused silica panel on a side of the first conductive layer;
a second fused silica panel on a side of the second conductive layer;
an anti-reflection coating on one or both of the first and second fused silica panels;
a switchable power supply selectively connected to the first and second conductive layers; and
a controllable switch controlling an application of alternating current (AC) from the switchable power supply to the two conductive layers, wherein AC applied to the first and second conductive layers aligns the liquid crystals and enables light to transparently pass through the liquid crystals, wherein:
when no AC is supplied to the first and second conductive layers, the liquid crystals are misaligned in the polymer, and the focal plane-array detector receives light diffused by the liquid crystals, and
the imaging system is configured to generate image data using the focal plane-array detector based on the light diffused by the liquid crystals and to calibrate the imaging system based on the generated image data in response to a schedule, a timer, or an image quality determination.
2 . The imaging system of claim 1 , wherein:
when AC is supplied to the two conductive layers, an electric field is created between the two conductive layers, the liquid crystals in the polymer are aligned, and the focal plane-array detector receives incident light transmitted through the aligned liquid crystals.
3 . The imaging system of claim 2 , wherein an image is acquired based on the incident light transmitted through the aligned liquid crystals.
4 . The imaging system of claim 1 , wherein the imaging system is calibrated using the image data generated based on the light diffused by the liquid crystals.
5 . The imaging system of claim 1 ,
wherein the anti-reflection coating is on one or both of the first and second fused silica panels.
6 . The imaging system of claim 1 , wherein the anti-reflection coating is a broadband anti-reflection coating.
7 . The imaging system of claim 1 , wherein the conductive layers comprise indium tin oxide or another conductive material.
8 . The imaging system of claim 1 , wherein the calibration is associated with one or more of a current and a voltage.
9 . The imaging system of claim 1 , wherein light collected by the one or more of the lens or the mirror is passed through the liquid crystals, wherein diffused light is received at the focal plane-array detector when no AC power is supplied to the two conductive layers, and wherein focused light is received at the focal plane-array detector when AC power is supplied to the two conductive layers.
10 . The imaging system of claim 1 , wherein the liquid crystals and conductive layers are contained within an optical system mounted between a light source and the one or more of the lens and the mirror.