Lens power F vs m for different values of P, calculated using the thin-lens formula of Eq. (8) (solid lines) and exact raytracing (data points) with a ray height of 20 μm. Ra = 11.2 mm, Rp = 6.0 mm, Ka = −4.5, Kp = −1.1, lens thickness T = 3.6 mm, P = 3, nc = 1.415 and ns = 1.37.