Figure 2. Incident direction of light. (a) incidence from the substrate side of the FZP, (b) incidence from the structure side of the FZP

From

The Focusing Characteristics on the Binary Phase Sub-wavelength Fresnel Zone Plate

Taikei Suyama

International Journal of Physics. 2019, 7(3), 86-90 doi:10.12691/ijp-7-3-3