Contents I. Introduction
Light has four main physical characteristics: intensity, wavelength, coherence, and polarization [1]. The human visual system is able to capture intensity and wavelength as brightness and color, respectively. However, it is oblivious to the polarization property of light. As a result, the mainstream image sensing systems are designed to mimic the human visual system by capturing only the intensity and wavelength property of light. It is known that the polarization property of light provides a lot of valuable information which is not available with the intensity/color imaging [2]. And the corresponding polarization image sensing systems have been demonstrated in various applications including biomedical imaging [3], [4], 3D shape reconstruction [5] and material classification [6], [7]. The recent advancements in the field of nanotechnology and nanofabrication have also made possible the capture of light’s polarization information, using a specific type of polarization sensor known as division of focal plane (DoFP) polarization image sensors. These sensors are highly compact by integrating metal nanowires offset by 45° as polarization grating, which is also named as micro-polarizer array [8]–[14]. These polarization sensors are arranged in a periodic pattern, namely a super-pixel, which despite having one more polarization channel, very well mimics the Bayer color filter array (CFA) with three wavelength channels (i.e. RGB) [15], as shown in Fig. 1.
Mainstream micro-polarizer array pattern of DoFP polarization image sensor.
