1. A lens structure, comprising: a first convex lens comprising a first curved side and a first flat side; a concave lens comprising a second curved side and a second flat side, the second curved side of the concave lens being arranged to face the first curved side of the first convex lens; a first space arranged between the first curved side of the first convex lens and the second curved side of the concave lens; and a Fresnel lens comprising a third flat side and a side comprising a faceted structure, the third flat side of the Fresnel lens being arranged to face the second flat side of the concave lens.