n1 = (sinc (θ⁄2))2 (1)
Provided that the photolithographic processing unit of the DOE surface is in the wavelength range (which is true outside of the UV range), the optical power (D) of a Variable Focus Moiré lens can be calculated as follows:
D = θ⁄Aπ (2)
Here θ, stands for the current twist angle of the DOEs and A denotes the clear aperture of the lens.
Equation 1 shows that the diffraction efficiency of the Variable Focus Moiré lens for a twist angle of ±90º (θ = ±π⁄2) is higher than 80%. For this lens with an aperture of the optical power range is as follows:
D = ±1⁄2A = ±25 Dpt
This means that the optical power of the Variable Focus Moiré lens is inversely proportional to the aperture. The NA has a constant value throughout the modulation of its optical power (NA = 0.24 in example described above).