Extended axial irradiances: Barker rings.

For extending focal depth we employ a set of transparent concentric rings, which are coded with the Barker sequences of length L. At the neighborhood of the paraxial focal plane, these transparent masks generate an axial uniform distribution, which is modulated with sinusoidal variations. For imaging applications, one can extend focal depth if the Barker length is congruent to unity modulo 4.

Two-conjugate zoom system: the zero-throw advantage.

We present the Gaussian design of a two-conjugate zoom system, which does not require any mechanical compensation. The device works in two stages. First, with fixed optical power, a lens images the pupil aperture, forming a pair of conjugate planes.

Reducing field depth: annular Hadamard masks.

For optically narrowing field depth, we explore the use of annular masks that are coded with the elements of Hadamard matrices. We show that with no further reduction of light throughput, these annular masks can enhance the influence of focus error on the modulation transfer functions (MTF). We report numerical evaluations of the irradiance point spread functions (PSFs), their associated MTFs, and of some digitally generated images.

Hopkins procedure for tunable magnification: surgical spectacles.

We analyze the use of two varifocal lenses, with fixed interlens separation, for achieving tunable magnification at a specific throw. Our discussion extends the Hopkins procedure circumscribed to the determination of fixed optical powers in a multilens system. We illustrate our results by presenting the Gaussian optics design of surgical spectacles, which have tunable magnification while generating virtual images with zero throw.

Schlieren masks: square root monomials, sigmoidal functions, and off-axis Gaussians.

By using an effective transfer function, one can describe conveniently the nonlinear mapping between an input thin transparent structure and its image irradiance distribution. This effective transfer function is useful for making sound comparisons between several spatial filters employed for phase rendering. Here, we unveil three nonconventional Schlieren techniques, which employ absorption masks whose amplitude distributions are described by square root monomials, by sigmoidal functions, or by off-axis Gaussian functions.