title: Comment on "Tunable three-dimensional intensity distribution by a pure phase-shifting apodizer".
abstract: In the past few years, many radially symmetric pupil masks have been designed for the control of the light intensity distribution near the geometrical focus of optical systems. A recent paper by Gao et al. [Appl. Opt. 44, 4870 (2005)] analyzed the performance of binary 0-pi phase-only masks for an incident beam with Gaussian amplitude. Some inaccuracies of the analysis concerning the evolution of the Strehl ratio with the mask parameters are corrected.
authors.affiliation: Departamento de Física Aplicada, Universidad de Cantabria, Santander, Spain. fernancv@unican.es
authors.forename: Vidal F
authors.initials: VF
authors.lastname: Canales
authors.forename: José E
authors.initials: JE
authors.lastname: Oti
authors.forename: Manuel P
authors.initials: MP
authors.lastname: Cagigal