Polarized pixelated filter array with reduced sensitivity to misalignment for polarimetric imaging

Patent metadata

Field	Value
Publication number	US-10969598-B2
Application number	US-201816162275-A
Country	US
Kind code	B2
Filing date	Oct 16, 2018
Priority date	Aug 26, 2015
Publication date	Apr 6, 2021
Grant date	Apr 6, 2021

Abstract

Polarized pixelated filter sub-array is reconfigured to reduce sensitivity to misalignment. The condition number increases more slowly than the standard polarized pixelated filter sub-array as the misalignment increases. In different embodiments, the filter sub-array is configured such that the condition number has a finite bound at ½ pixel misalignment. The angular values of the polarizer filter array are determined to minimize the sensitivity of the condition number of the data reduction matrix to misalignment. This can be achieved by selecting angular values that minimize the expected value of the condition number E(CN) over the range of misalignment.

First claim

We claim:

1. A polarized pixelated filter array for selectively polarizing electromagnetic radiation for use with a pixelated detector having detector pixels in x and y directions for which sub-arrays of three or more (P) detector pixels are read out and processed to form a polarimetric image, said polarized pixelated filter array comprising one or more filter sub-arrays, each filter sub-array comprising:
three or more (Q) filter pixels in the x and y directions where Q>=P, each grouping of P adjacent filter pixels of the Q filter pixels in the filter sub-array including at least three pixels configured to impart linear polarizations of different angular values or at least two pixels configured to impart linear polarizations of different angular values and at least one unpolarized pixel, wherein said angular values are set to minimize an expected value of a condition number (CN) of a data reduction matrix of the filter sub-array to misalignment of the polarized pixelated filter array in the x and y directions relative to the pixelated detector where the misalignment is modeled as a random variable with a non-zero probability distribution p ma (x,y) of misalignment with a range of misalignment in the x and y directions.

2. A polarized pixelated filter array for selectively polarizing electromagnetic radiation for use with a pixelated detector having detector pixels in x and y directions for which 2×2 sub-arrays of detector pixels are read out and processed to form a polarimetric image, said polarized pixelated filter array comprising one or more filter sub-arrays, each filter sub-array comprising:
N×N filter pixels in the x and y directions where N>=2, each grouping of 2×2 filter pixels of the N×N filter pixels in the filter sub-array including at least three pixels configured to impart linear polarizations of different angular values or at least two pixels configured to impart linear polarizations of different angular values and at least one unpolarized pixel, wherein said angular values are set to minimize an expected value of a condition number (CN) of a data reduction matrix of the filter sub-array to misalignment of the polarized pixelated filter array in the x and y directions relative to the pixelated detector where the misalignment is modeled as a random variable with a non-zero probability distribution p ma (x,y) of misalignment with a range of misalignment in the x and y directions.

3. The polarized pixelated filter array of claim 2 , wherein N=3.

4. The polarized pixelated filter array of claim 2 , wherein each said grouping of 2×2 filter pixels includes at least one unpolarized pixel.

5. The polarized pixelated filter array of claim 2 , wherein the range of misalignment spans 0 to ½ pixel in the x or y directions.

6. The polarized pixelated filter array of claim 2 , where N=2, wherein each grouping of 2×2 filter pixels includes three pixels configured to impart linear polarizations of different angular values and a fourth filter pixels having an angular value equal to the angular value of one of said three pixels.

7. The polarized pixelated filter sub-array of claim 2 , wherein N=4, said filter sub-array comprising:
a plurality of filter pixels arranged in a 4×4 grid format in x and y directions, including 8 filter pixels that impart a linear polarization of a certain angular value and 8 unpolarized, U, filter pixels, wherein the relative angular values for the 4×4 grid format are:

U
⁢

70
⁢
°

⁢

U
⁢

110
⁢
°

215
⁢
°

U
⁢

5
⁢
°

⁢

U
⁢

U
⁢

140
⁢
°

U
⁢

20
⁢
°

⁢

200
⁢
°

U
⁢

45
⁢
°

U
.

⁢

8. An imaging system, comprising:
a polarized pixelated filter array having filter pixels in x and y directions;
a pixelated detector having detector pixels in x and y directions for which sub-arrays of three or more (P) detector pixels are read out and processed to form a polarimetric image,
wherein a misalignment of the polarized pixelated filter array in the x and y directions relative to the pixelated detector is modeled as a random variable with a non-zero probability, distribution p ma (x,y) of misalignment with a range of misal

Assignees

• Raytheon Co

Inventors

• Fest Eric C
• Leigh Jon E

Classifications

• G02B5/3025

  Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state (G02B5/3008, G02B5/3016 take precedence) · CPC title

• G02B27/286 Primary

  for controlling or changing the state of polarisation, e.g. transforming one polarisation state into another (G02B5/3083 takes precedence; light guide coupling means utilising polarising elements G02B6/34) · CPC title

• G01J4/04

  Polarimeters using electric detection means (G01J4/02 takes precedence) · CPC title

• G06T7/344

  involving models · CPC title

• G06T2207/10048

  Infrared image · CPC title