An optical filter structure for an imager which has customized sub-wavelength elements used to maintain the filter characteristics accordingly across a photo-conversion device to optimize the structure for the angle of incidence as it changes across the imager photo-conversion device. In particular, the layout (e.g., grating period among other parameters) of the sub-wavelength elements used in the structure design are customized to change with the angle of incidence of the optics used to project the image. The sub-wavelength elements are typically built by high resolution lithographic processes such as optical or imprint lithography.