Examples of an imaging system for use with a head mounted display (HMD) are disclosed. The imaging system can include a forward-facing imaging camera and a surface of a display of the HMD can include an off-axis diffractive optical element (DOE) or hot minor configured to reflect light to the imaging camera. The DOE or hot minor can be segmented, for example, with different segments having different angles or different optical power. The imaging system can be used for eye tracking, biometric identification, multiscopic reconstruction of the three-dimensional shape of the eye, etc. Methods for manufacturing angularly segmented optical elements are also provided. The methods can include injection molding.