In this paper, we describe the design, modeling, fabrication, and optical characterization of the first micropolarimeter array enabling full Stokes polarization imaging in visible spectrum. The proposed micropolarimeter is fabricated by patterning a liquid-crystal (LC) layer on top of a visible-regime metal-wire-grid polarizer (MWGP) using ultraviolet sensitive sulfonic-dye-1 as the LC photoalignment material. This arrangement enables the formation of either micrometer-scale LC polarization rotators, neutral density filters or quarter wavelength retarders. These elements are in turn exploited to acquire all components of the Stokes vector, which describes all possible polarization states of light. Reported major principal transmittance of 75% and extinction ratio of 1100 demonstrate that the MWGP’s superior optical characteristics are retained. The proposed liquid-crystal micropolarimeter array can be integrated on top of a complementary metal-oxide-semiconductor (CMOS) image sensor for real-time full Stokes polarization imaging.

We report a micropolarizer array technology exploiting “guest-host” interactions in liquid crystals for visible imaging polarimetry. We demonstrate high resolution thin micropolarizer arrays with a 5 μm × 5 μm pixel pitch and a thickness of 0.95 μm. With the “host” nematic liquid crystal molecules photo-aligned by sulfonic azo-dye SD1, we report averaged major principal transmittance, polarization efficiency and order parameter of 80.3%, 0.863 and 0.848, respectively across the 400 nm – 700 nm visible spectrum range. The proposed fabrication technology completely removes the need for any selective etching during the fabrication/integration process of the micropolarizer array. Fully CMOS compatible, it is simple and cost-effective, requiring only spin-coating followed by a single ultraviolet-exposure through a “photoalignment master”. This makes it well suited to low cost polarization imaging applications.

We report a superior high-resolution micropolarizer array fabrication technology that combines a linear polarizer with a micropatterned liquid-crystal (LC) cell. A $2\mu \mathrm{m}$ pitch is achieved by using UV light to define the orientation of the micropolarizer elements. Reported experimental results validate the concept of high-performance photoaligned LC micropolarizer arrays with major principal transmittance of $\sim 80\%$ and extinction ratio as high as $\sim 3200$ $\left(35\mathrm{dB}\right)$.

In this paper, a 0.18 μm CMOS color processing scheme based on NPNP-triple-junction structure is proposed to achieve real-time skin detection. The need for building complex demosaicing circuitry is completely eliminated, which dramatically reduces the fabrication cost and simplifies the pixel space sampling algorithm. In addition, real-time detection is enabled through the use of logarithmic readout mode and Gilbert normalization cell. The fabricated chip and related measurement results have verified the concept of a compact, low cost, CMOS fully compatible micro-sensor suitable for skin detection.