Enhancement of imaging performance of a variable focus Fresnel zone plate based on a single, binary, phase-only SLM

• Published in: Optics communications 2001-06, Vol.193 (1), p.27-38
• Main Authors: Paige, E.G.S., Sucharov, L.O.D.
• Format: Article
• Language: English
• Subjects: Binary phase-only SLM; Exact sciences and technology; Filters, zone plates, and polarizers; Fresnel zone plate; Fundamental areas of phenomenology (including applications); Multi-planar imaging; Optical elements, devices, and systems; Optical processors, correlators, and modulators; Optics; Physics; Variable focus component
• ISSN: 0030-4018; 1873-0310
• DOI: 10.1016/S0030-4018(01)01178-6

It is shown that the imaging performance of a variable focus optical system based on a single, binary, phase-only spatial light modulator (SLM) can be improved in important respects by combining it with a fixed phase mask with either two or four phase levels separated by π/2. With the SLM encoded as a modified Fresnel zone plate, the images associated with one member of each of the pair of foci, ± f, ± f/3, ± f/5, etc. are deflected and blocked by a stop enabling a single image plane to dominate the performance. Analytical expressions are derived for the peak amplitudes of the point spread functions of a simple imaging system. The simulated performance of a variable focus system is reported in which the intensity in a single selected image plane, scanned in the z-direction, is about an order of magnitude greater than other image planes and in which the scan range is approximately doubled by switching between + f and − f foci.