Telemedicine based screening of infants at risk for retinopathy of prematurity.

Retinopathy of Prematurity (ROP) is a major risk for permanent visual loss in extreme prematures. In stage 3+ (zone I and II), defined as threshold disease, the risk for retinal detachment with subsequent blindness is about 50% without treatment, compared to only a few percent with laser photoablation. Visualisation and interpretation of the critical retinal changes requires a high degree of expertise. Therefore, screening by general ophthalmologists will not identify all cases at threshold necessary to prevent blindness in as many infants as possible. The development of a new digital wide-field camera system (RetCam 120) allows documentation of nearly the entire retina within minutes. Recently, sensitivity, specificity, positive predictive power and negative predictive power have been evaluated to be high. Data collection is also possible by trained staff of the neonatal care units. Data can be transferred electronically, even though it could be transferred through physical transport. Analyzing the data in a central reading center specialized in the treatment of ROP will allow optimal timing of treatment and thus salvage vision in more infants. In addition, unnecessary referrals that are not only expensive but put also stress on the very vulnerable prematures can be avoided. At present, efforts are made to realize a pilot project in Eastern Bavaria that will test the potentials of telemedicine based screening for ROP. In addition, the potential of the system will be evaluated in other neuroophthalmological diseases.

Low-cost, high-resolution, single-structure array telescopes for imaging of low-Earth-orbit satellites.

Telescopes that are designed for the unconventional imaging of near-Earth satellites must follow unique design rules. The costs must be reduced substantially over those of the conventional telescope designs, and the design must accommodate a technique to circumvent atmospheric distortion of the image. Apertures of 12 m and more along with altitude-altitude mounts that provide high tracking rates are required. A novel design for such a telescope, optimized for speckle imaging, has been generated. Its mount closely resembles a radar mount, and it does not use the conventional dome. Costs for this design are projected to be considerably lower than those for the conventional designs. Results of a design study are presented with details of the electro-optical and optical designs.

High accuracy interferometric measurements of electron-beam pumped transverse-flow laser media with 10-microsec time resolution.

Electron-beam pumped transverse flow lasers suffer from turbulence and acoustic wave induced optical perturbations which degrade optical beam quality. Existing diagnostic technologies give limited low resolution information about these phenomena. The successful use of the high resolution digital heterodyne interferometer to obtain high quality measurements of these phenomena is described. The interferometer was equipped with multiple detectors with parallel outputs, each simultaneously reporting optical path difference measurements. Phase resolution of lambda/300 was demonstrated simultaneous with a 10-microsec time resolution. Substantial and unique information on flow and acoustic phenomena was obtained that was not previously available.

Real-time digital heterodyne interferometry: a system.

A system for obtaining real-time optical path difference maps is described. Results of applications to characterize thermally driven optical phenomena and active optical components are presented. Demonstrated performance parameters include a serial data acquisition rate of 50-microsec/point, spatial resolution to 500 points/line, and phase accuracy of lambda/70.

High-performance real-time heterodyne interferometry.

A novel system for real-time heterodyne interferometry of extended objects is demonstrated. Featured in this system is the direct measurement of the optical path difference, eliminating the sometimes troublesome interpretation of the fringe patterns of traditional interferometry. High spatial and temporal resolutions are available in real time for a properly instrumented system. The concept, its performance, and applications are presented along with results from a breadboard system, where phase accuracy of better than lambda/100 is demonstrated.

Beam quality of acousto-optic frequency shifters.

The beam quality of the diffracted wave from a bulk acousto-optic frequency shifter has been accurately measured. High accuracy in measuring the output-phase profile was achieved by a unique utilization of heterodyne interferometry. Results for glass and PbMoO(4) deflectors show no discernible beam-quality degradation attributible to the acousto-optic interaction to within 0.01 wave rms at 647.1 nm.