Fourier transform pupil functions for modifying the depth of focus of optical imaging systems.

We use a Fourier transform approach to design pupil functions that modify the axial depth of focus for an optical system. We extend previous research in several ways. We first extend the depth of focus to 4 cm for a 38 cm focal length lens. We show that the transverse size of the focused beam is the same as for an open pupil. We then multiply the pupil function by a circular harmonic window function. The entire depth of focus is now characterized by a vortex beam. Finally we multiply our original pupil function by an edge-enhancing window function. Now the pupil function produces two sharp focus spots at the locations corresponding to the edges of the rectangle function.

High diffraction efficiency from one- and two-dimensional Nyquist frequency binary-phase gratings.

We examine the diffraction properties of one- and two-dimensional binary-phase gratings encoded onto pixelated liquid crystal displays (LCDs). We find that the first-order diffracted intensity from these binary-phase patterns can reach 100% of the zero-order intensity when the period of the grating approaches the Nyquist limit of the LCD. Experimental results show excellent agreement with theoretical predictions. This is a surprising result that has a number of implications for the encoding of diffractive optical elements.

Sidelobe contrast reduction for optical vortex beams using a helical axicon.

We present a new approach for generating an optical vortex pattern with reduced sidelobes without increasing the radius of the vortex and without excessive energy loss. Our technique combines the spiral phase plate with a weak axicon to form a helical axicon. Experimental results using a liquid crystal display agree with theory.

Tailoring the depth of focus for optical imaging systems using a Fourier transform approach.

We show how to tailor the depth of focus for an optical system using pupil functions obtained from a Fourier transform approach. These complex amplitude and phase pupil functions are encoded onto a single liquid-crystal spatial light modulator. Experimental results show excellent agreement with theory and indicate the power of this approach.