• Fresnel zone plate can be prepared by drawing concentric circles on a transparency.
• The differences in lengths of consecutive radiuses become smaller as the radius become bigger.
• Consecutive radiuses relate to each other as the square roots of the positive integers: 1,2,3,4,5, ...
• Every second ring is painted black, so that light can pass through every other ring.

Figure 10.5: Fresnel Zone Plate

The Transparency can be photographed and reduce in proportion to achieve the required size of the optical element.

The focal length of Fresnel zone plate is determined by the size of the inner circle, and the wavelength in use.

Unlike regular lens, the focal length of Fresnel zone plate is strongly dependent on wavelength, so the same plate can not be used for different wavelengths to achieve the same focal length.

We shall see that such a problem exist in all the diffractive optical elements (DOE) which are elements of Binary optics.