We report the optical characterization of a metal wiregrid micropolarizer array for IR imaging polarimetry. The micropolarizers are designed for operation in the $1.5–5.0\mu \mathrm{m}$ band with a specially designed thin $\mathrm{Si}{\mathrm{O}}_2$ layer between the silicon substrate and the wiregrids to improve the performance at the shorter wavelengths. Deep-UV projection lithography is used to fabricate $140\text{-}\mathrm{nm}$ -deep wiregrids with a $400\mathrm{nm}$ period. The extinction ratio and the transmission coefficient are measured with a tunable IR laser. A TM transmission coefficient greater than 70% with an extinction ratio greater than ${10}^4$ is achieved for the midwave-IR region while maintaining an extinction ratio better than ${10}^2$ for the near-IR region above $1.5\mu \mathrm{m}$ .