The resolution of conventional space telescopes is determined by the size of their primary mirror. However,
quality high resolution images can be obtained using inexpensive micro-satellite carrying an optical synthetic
aperture telescope. Noise, quantization (A to D) errors and aberrations due to imprecise location
and/or deformation of optical parts may all degrade the accuracy of the raw, unprocessed, individual images
and thus also the quality and resolution of the final synthesized image. These are analyzed in this paper.
Sample simulated images are presented, as well as some design and processing rules for such systems.
The resolution of conventional space telescopes is limited by the size of their aperture. High resolution telescopes
must have large aperture primary mirrors - heavy, expensive and costly to deliver to orbit. In contrast,
micro-satellites are small, relatively inexpensive, and are often "hitch-hiked" with other payload to
orbit. However, the size of micro-satellites limits them to small aperture optics. By combining multiple images
from a suitably-designed telescope with several small mirrors and digitally post-processing the combined
image, it is possible to obtain higher resolution. The optical layout and the digital post-synthesis for
these proposed micro-satellite telescopes are presented and analyzed.
Cat-eye-array retro-reflectors, combining a lenslet array with a reflective surface at the common focal plane of the lenslets, are widely used due to their simple structure and low cost. While for many applications the performance (brightness, acceptance angle range and directionality) is acceptable, others could benefit from better performance. Improving these retroreflectors is difficult because their simplicity results in too few degrees of freedom. Here, we show how the use of one or two diffractive surfaces can significantly increase the brightness of the reflected beam and/or the acceptance angle while still allowing inexpensive manufacturing by molding or replication. Specifically, we focus here on one potential application of cat-eye-array retro-reflectors: semipassive optical communication units. Semi-passive communication units combine a retroreflector
with a light modulator. The directional auto-aligned retro-reflected signal enhances security and power efficiency. Furthermore, many modulators use very low power: far lower than light emitter. Modulated retro-reflectors have already been demonstrated for space and military communication. Here we focus on a different application: optical smart cards. These devices described elsewhere, can be used, for example, for access control identification or as non-contact secure teller machine ID. Such devices must have an optical modulator in the optical path, so the effect of the modulator must also be accounted for in the design. As a consumer product, low cost manufacturability is another requirement. Design examples are presented.
Optical smart cards are devices containing a retro-reflector, light modulator, and some computing
and data storage capabilities to affect semi-passive communication. They do not
produce light; instead they modulate and send back light received from a stationary unit.
These devices can replace contact-based smart cards as well as RF based ones for applications
ranging from identification to transmitting and validating data. Since their
transmission is essentially focused on the receiving unit, they are harder to eavesdrop than
RF devices, yet need no physical contact or alignment. In this paper we explore optical
design issues of these devices and estimate their optical behavior. Specifically, we analyze
how these compact devices can be optimized for selected application profiles. Some of the
key parameters addressed are effective light efficiency (how much modulated signal can be
received by the stationary unit given the amount of light it transmits), range of tilt angles
(angle between device surface normal to the line connecting the optical smart card with the
stationary unit) through which the device would be effective, and power requirements of the
semi-passive unit. In addition, issues concerning compact packaging of this device are discussed.
Finally, results of the analysis are employed to produce a comparison of achievable
capabilities of these optical smart cards, as opposed to alternative devices, and discuss potential
applications were they can be best utilized.
In this work, we elaborate on the compromise between the efficiency of the multiprocessor computer architecture for handling large classes of computing tasks and the good performance of optics for implementing shift invariant operations, in particular convolution. We derive a class of processors, optoelectronic cellular automata that can efficiently implement intensive, low level vision tasks in a time compatible with application constraints up to standard video rates. As one illustration, a parallel simulated annealing task performing motion detection on an image sequence is demonstrated.
In this work, we elaborate on the compromise between the efficiency of a multiprocessor computer architecture for handling large classes of computing tasks and the good performance of optics for implementing shift invariant operations, in particular convolution. We derive a class of processors, optoelectronic cellular automata, that can efficiently implement intensive, low level vision tasks in a time compatible with application constraints up to standard video rates. As one illustration, a parallel simulated annealing task performing motion detection on an image sequence is demonstrated.
An important factor in the success of electronic technology in the last few decades is the continuous drive for miniaturization: computing power that used to require a hall full of equipment fits nowadays comfortably in a notebook sized machine. The size of basic optical instruments, however, remained almost unchanged. Today, it is the size of optical devices and subsystems that limits further miniaturization of opto-electronic systems. Here, we describe and demonstrate optical configurations that enable us to design and fabricate very compact optical systems, based on the use of multiple micro-lens arrays. One such system is the multiple lenslet array imager (MLAI) that allows the distance between an object and its full size optical image to be as small as few centimeters, regardless of the size of the object. Another system is the lenslet array holographic correlator/convolver (LAHC), where we combine multiple lenslet arrays and a holographic filter to obtain a very compact optical correlator. Issues in micro-lens arrays fabrication and selected applications are discussed, and some laboratory demonstrations are presented.
Multiple lenslet array imagers (MLAIs) are compact optical systems made of several cascaded lenslet arrays. These systems can provide images that are many times larger than their total object to image distance. Here we describe a new variant of the MLAI that provides control over the optical transfer function (OTF) of the imaging process. This OTF synthesis capability makes it possible to control the resolution of MLAIs, as well as to use them as correlators or convolvers in optical information processing systems. Several variants of this new device, results from an experimental demonstration, and an analysis of its key performance issues, are presented.