1. A camera, comprising: a first substrate having a convex refractive element; a second substrate having a concave refractive element; a separation between the first to second substrates, the separation including an air gap between convex refractive element and the concave refractive element; and a third substrate having a detector array thereon, the concave refractive element being closer to the detector than the convex refractive element, at least two of the first to third substrates being secured at a wafer level.