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It looked like I was staring into the compound lens on the eye of an insect.

The self-assembling petals collectively act as a compound lens that focuses light much like a fly's eye.

Chromatic aberration is easily cured by using an achromatic or compound lens made by cementing together two lenses of crown and flint glass respectively, as in Fig.

A compound lens is needed, made up of a crown glass convex element, B, and a concave element, A, of flint glass.

With a compound lens, such as a 'Petzval' combination, this method does not hold good, as the optical centre of such a lens is not necessarily midway between its two components.