2-Cam LWIR imaging Stokes polarimeter

Abstract

A 2-Cam micro-bolometer imaging polarimeter operating in the LWIR is presented. The system is capable of snapshot imaging Stokes polarimetry in any one channel (S 1 , S 2 , or S 3 ) by taking two simultaneous measurements of a scene. For measurements of S 1 or S 2 , the instrument relies on a specially optimized wire-grid beam-splitter. For measurements of S 3 , a form birefringent quarter-wave retarder is inserted into the optical path. Specifics associated with the design of the wire-grid beam-splitter and the form birefringent quarter-wave retarder will be overviewed, with inclusion of RCWA simulations. Calibration and simulation procedures, as well as calibration targets, will be highlighted, and initial data from the instrument are presented.

Opto-Electronics Review

“…In the case of division of amplitude polarimeters, beam-splitting elements are used to divide the incoming radiation into separate detection branches, each of which is dedicated to the measurement of a different Stokes parameter. The beam-splitting elements can be of polarizing or non-polarizing variety [4]. This solution was also used in the polarimetric camera, Spyder, manufactured by Polaris Sensor Technologies, Inc. [4].…”

“…The beam-splitting elements can be of polarizing or non-polarizing variety [4]. This solution was also used in the polarimetric camera, Spyder, manufactured by Polaris Sensor Technologies, Inc. [4]. Division of amplitude polarimeters are characterized by large dimensions and high implementation costs, as they require multiple detection matrices (minimum two).…”

“…Division of amplitude systems is difficult to align properly due to a large number of alignment degrees of freedom and strict requirements on the image alignment. According to different authors, images should be aligned at least within ¼ of a pixel, some authors suggesting even 1/10 of a pixel [34] what is considered to be virtually impossible to achieve for this kind of system [4,24,27]. Moreover, this alignment is difficult to maintain longterm especially in a wide range of ambient temperatures.…”

“…Imaging polarimetry has been a subject of extensive research in leading scientific centres [1][2][3][4] in recent two decades. In astronomy, imaging polarimetry has been used since the 1970s.…”

Optimal snapshot full-Stokes imaging polarimeter in the visible band based on division-of-aperture

“…Such information of a light beam can be described by means of the Stokes vector 𝑆𝑆 ⃗ and its detection requires a series of measurements using specific polarization elements in the optical path to project the input polarization state of light into their associated intensity measurements. Many studies have been conducted to design a full Stokes polarimeter and four main architectures are employed: division of time 5 , division of amplitude 6 , division of focal plane 7 and division of aperture 8 . Among the main drawbacks of the different configurations, it can be found the misalignment between elements, the artifacts of movement, or being unable to retrieve the complete Stokes vector.…”