Optical power of a lens is a quantity that is inversely proportional to the focal length; therefore, it can be calculated in diopters.
It is denoted by the letter D, and the unit of optical power is the diopter. 1 diopter is the optical power with a focal length of 1 meter.
In the SI system, the unit of measurement for optical power is the inverse meter.[dpt] = [1/m] = [m⁻¹]
Lenses that converge and diverge differ in their primary functions. This means that their optical powers will differ. For converging lenses, a positive sign is used before the optical power, while for diverging lenses, a negative sign is used.
If you need to calculate the optical power of a system consisting of two lenses, you can use the formula:
D = D1 + D2 – dD1D2,
D – the final optical power,
D1 – the optical power of the first lens,
D2 – the optical power of the second lens,
d – the distance between the lenses.
For a system of thin lenses, the power is calculated as the algebraic sum of the optical powers of each lens:
D = D1 + D2 + D3 + … + Dn.