Ty Martinez

Adaptive optical zoom

In order to optically vary the magnification of an imaging system, continuous mechanical zoom lenses require multiple optical elements and use fine mechanical motion to precisely adjust the separations between individual or groups of lenses. By incorporating active elements, such as liquid crystal spatial light modulators or deformable mirrors, into the optical design, we can eliminate the need to change the spacing between lenses and create an imaging system with variable optical magnification that has no macroscopic moving parts.

Foveated, wide field-of-view imaging system using a liquid crystal spatial light modulator.

The field-of-view (FOV) of a simple imaging system can be dramatically improved using a liquid crystal spatial light modulator (SLM). A SLM can be used to correct the off-axis aberrations that often limit the useful FOV of an imaging system giving near diffraction-limited performance at much larger field angles than would otherwise be possible. Foveated imaging refers to the variation in spatial resolution across the image caused by using the SLM in this application, and it is useful in reducing bandwidth requirements for data transmission.

Foveated imaging demonstration

A wide field-of-view (FOV), theoretically diffraction-limited imaging system is demonstrated using a single positive lens (a singlet), a reflective liquid crystal spatial light modulator (SLM), a turning mirror and a CCD camera. The SLM is used to correct the off-axis aberrations that would otherwise limit the useful FOV of our system. Foveated imaging refers to the variation in spatial resolution across the image caused by using the SLM in this manner.

Active multimodal control of a floppy telescope structure

Telescope structures are typically required to attain a certain degree of mechanical rigidity in order to achieve the desired optical performance goals, yet there are many applications where weight is either at a premium or local conditions exist that pre-empt optimal mechanical stability requirements. What is needed is a system which can sense and compensate for the opto-mechanical instabilities and correct them in real-time, preferably without stealing light from the optical system. We propose using tiny MEMS-based inertial reference sensors to measure the structural dynamics, and, using an appropriate model and coordinate transformations, correct in real-time the tip/tilt, focus, and possibly higher order errors of the optical system aberrations using MEMS-based deformable mirrors and/or our own tip/tilt + piston mirrors.

Non-mechanical zoom system

In order to optically vary the magnification of an imaging system, mechanical zoom lenses, such as those found on 35mm cameras, require multiple optical elements and use cams or gears to adjust the spacing between individual or groups of lenses. By incorporating active elements in the optical design, we can eliminate the need to change lens separations and create an imaging system with variable optical magnification that has no macroscopic moving parts.

Dynamic holography for high-dynamic-range two-dimensional laser wavefront control

Dynamic holography is demonstrated as a technique for high- dynamic-range, multi-function laser wavefront control. In this paper, we describe three variations for hologram generation and display. These include all-optical holography for severe aberration compensation, computer-processed holography for high-optical-efficiency severe aberration compensation and computer-generated holography for multi- function laser wavefront control including dynamic tip, tilt, focus and aberration control. A prototype hologram display system operates with total optical efficiencies up to 93% and with refresh rates on the order of 10 Hz. The prototype system has resolution sufficient to introduce about 200 waves of diffractive wavefront control at 532 nm optical wavelength.

Holographic compensation of severe dynamic aberrations in membrane-mirror-based telescope systems

Real-time holography compensates for severe aberrations in membrane-mirror based telescope systems. Laboratory demonstrations in both imaging and beam projection have been conducted. Prototype optically addressed liquid-crystal spatial light modulator devices, developed and adapted for this application, are demonstrated with significantly improved diffraction efficiencies.

System concept and some characteristics of the coupled-cavity laser system for active target tracking

We performed architecture and design analyses of coupled-cavity laser systems to arrive at a concept for tracking distant objects. We also conducted an experimental study of such a system using a pulsed ruby laser as a prototype for the laboratory tests. Both laser cavities were coupled through the dynamic holographic grating. Special attention was paid to characterization of the coupled-cavity laser system and its operation. In particular, we studied the formation of holographic grating that serves to couple the cavity; the slope efficiency of the master and slave arms and their dependence upon cavity parameters. The resulted experimental data and analyses verified the tracking principle and proved the feasibility of the proposed phase-conjugate double cavity laser system for tracking moving object at distance with high accuracy.

Correction of large dynamic aberrations by real-time holography using electro-optical devices and nonlinear optical media

Real-time holography compensates for severely aberrated primary mirrors in large aperture telescope systems. A prototype optically addressed liquid-crystal spatial light modulator device developed for this application is demonstrated with short response times, approximately 600 microsecond(s), and high diffraction efficiencies approaching 40%.

Wide-field-of-view foveated imaging system using a liquid crystal spatial light modulator

We have successfully demonstrated a simple, wide field-of- view, foveated imaging system utilizing a liquid crystal spatial light modulator (SLM). The SLM was used to correct the off-axis aberrations that otherwise limited the useful field-of-view (FOV) of our system. Our system mimics the operation of the human eye by creating an image with variable spatial resolution and could be made significantly smaller and more compact than a conventional wide FOV system. It may be useful in applications such as surveillance, remote navigation of unmanned vehicles, and target acquisition and tracking, or any application where size, weight, or data transmission bandwidth is critical.