Tasso R. M. Sales

Fundamental limits of optical superresolution

Increasing the resolving power of optical systems beyond the limits imposed by diffraction, or superresolution, has considerable theoretical as well as practical interest. Several schemes have been proposed to achieve superresolution with reasonable success, but there are no criteria that enable one to determine what improvement can ultimately be attained for a certain level of resolution. We have determined fundamental limits imposed on the performance of any superresolution strategy. A brief analysis indicates that current optical-superresolution techniques can still have their performance considerably augmented.

Axial superresolution with phase-only pupil filters

A novel filter design for axial superresolution based on a phase-only pupil function is introduced. Solutions for confocal scanning microscopy indicate that the phase-only design reduces the axial spot size by a factor of 2.

LED illumination control and color mixing with Engineered Diffusers

We propose and demonstrate the use of Engineered Diffusers for control and distribution of LED light for general lighting applications. These diffusers are based on refractive microstructures and enable the efficient use of energy by controlling light propagation and directing it to specific regions of space. The microstructures are generally microlens-based arrays with each microlens elements individually designed to meet the desired scatter properties. In addition to light control, Engineered Diffusers can be used for RGB mixing to produce white light with variable color temperature, depending on the RGB content of the source. A single Engineered Diffuser component can be used for efficient color mixing and illumination control. We also discuss the fabrication of Engineered Diffusers by means of a single-point laserwriting method with capability to manufacture the deep refractive structures needed for LED beam shaping.

Deterministic microlens diffuser for Lambertian scatter

We demonstrate the application of deterministic microlens diffusers to generate Lambertian scatter in transmission with high efficiency. Two identical surface diffuser elements are used in tandem to spread light with constant radiance. Design methods are discussed and experimental demonstration is presented.

Beam shaping and homogenization with random microlens arrays

We describe the use of random microlens arrays for beam shaping and homogenization applications. Within the array, the vertex height and radii of curvature (in the two orthogonal surface directions) of each lens are randomized. We present theoretical and experimental data for these diffusing structures.

Recent advances in microlens-based projection display screens

In the past few years the microdisplay-based projection television market has been quickly spreading over what used to be the domain of CRT technology. The demand for larger display sizes and improved image quality, together with more accessible pricing is aggressively driving the transition to microdisplays. The screen is the component of the projection system that directly conveys the visual information to the user, responsible for distributing the luminous energy from the light engine. However, the projection screen is far from a simple diffuser and todays performance requirements for display systems require sophisticated screens to meet the resolution, transmission efficiency, and contrast required by visual displays.

Lightguide with controlled numerical aperture for general illumination

Lightguide devices are commonly used in a large number of applications such as light-delivery systems, illumination, and displays. The general approach is to outcouple light from the lightguide without concern for its propagation properties within the guiding material. We introduce the concept of a lightguide with controlled numerical-aperture as it propagates within the guiding substrate and demonstrate the advantages with this approach, compared to other methods commonly used. We also demonstrate the application of our lightguide technology for general illumination with controlled light distribution and high efficiency.

Persistence of scaling behaviour in the Game of Life

The persistence of scaling laws in the evolution of the automaton Game of Life from a correlated configuration is investigated. It is found that even for a highly correlated initial state, the temporal evolution is able to preserve scaling relations as observed for uncorrelated states, although with possibly discordant critical exponents. The difference can be accounted for by introducing a stochastic component in the transition rules, which at the same time establishes a connection with the possible convergence of Life to a self-organized critical state.