What can adaptive optics do for a scanning laser ophthalmoscope ?

By compensating for the aberrations in the eye that cause blur, the adaptive optics scanning laser ophthalmoscope (AOSLO) yields high-magnification, high-resolution, real-time images of the living human retina. Features as small as single cone photoreceptors can be resolved, single leukocytes are recorded in real time as they pass through the smallest retinal capillaries, and the optical sectioning capability can be used to visualize independent layers of the retinal tissue ranging from the nerve fiber layer, through the blood vessels to the photoreceptors. The use of AO technology not only enhances the breadth of applications of conventional SLOs, but it facilitates a host of new applications. Here we provide an overview of AOSLO performance and its applications, including two clinical examples. Finally, we preview two novel applications; one where the AOSLO is used to present AO-corrected stimuli directly onto the retina while simultaneously recording their exact retinal position, and a second application where AOSLO videos are used to provide very precise, high-frequency measures of eye movements.

Optical attenuation by periodic microdistortions of a sensor fiber.

The attenuation of optical power in a graded-index multimode fiber subjected to periodic microdistortions has been measured. The noncommunication fiber (designated the sensor fiber) had a small numerical aperture and a large core diameter, resulting in a large coupling wavelength and an enhanced sensitivity to microdistortion forces. The linewidth of the fundamental attenuation peak is in excellent agreement with that predicted by theory without the need to introduce a correlation length. The amplitude and force dependence of the attenuation measured at the fundamental peak is also in excellent agreement with theory. The inferred distortion force versus distortion amplitude curve is a straight line, as predicted by elasticity theory.

Modular infrared microspectrometer with cryosampling capabilities.

A modular infrared spectrometer with microsampling and cryosampling capabilities has been designed, constructed, and tested. The main design features and preliminary results are discussed, and some strengths of the final instrument, when used in the optical characterization of superconducting materials, are presented.

Improved sensitivity in sensor fibers by the proper source/coating selection.

The dependence of the optical attenuation on the fiber coating has been measured for a sensor fiber subjected to periodic microbending. The dependence on the spectral characteristics of the selected light sources is also addressed and the proper source/coating combination is discussed. Results indicate that the proper selection of this combination is of crucial importance in the design, development, and performance of fiber optic sensors in which intensity modulated microbending transducers are considered. A combination of a short wavelength for the light source and a fiber coated with a hard, elastomeric material seems to be the optimal selection for enhancing the sensitivity in controlled microbending experiments with applications to fiber optic sensors. The highest sensitivity to microbending was obtained for a nylon coated fiber and using a He-Ne laser at 632.8 nm.