An object viewed via reflection from a mirrored surface is often perceived by the observer to be located behind the mirror's surface. The image of this object behind the mirror is known as its virtual image. Conventional methods for determining the location and shape of a virtual image for non-planar mirrors are complex and impractical unless both the observer and object are near the optical axis. We have developed a technique designed to be simple and practical for determining the location of a virtual image in a non-planar mirror far from the optical axis. Results using this technique were compared with known results from geometric optics for an object point on the optical axis of a parabola and for an object point imaged off the optical axis of a spherical mirror. These results were also in agreement with experimental measurements for a hemispherical mirror viewed at large angles with respect to its optical axis. This technique has applications for display devices or imaging tools utilizing curved, mirrored surfaces.

The reflectance of a surface can be altered by controlling the concentration of dye ions in a region adjacent to an optically transparent and electrically conductive thin film. We present a method for nonmechanical light deflection achieved by altering the reflectance of a diffraction grating, an approach that creates new diffraction peaks that lie between those associated with the original grating spacing. We have demonstrated this effect by applying an electrical potential difference between interdigitated indium-tin oxide (ITO) electrodes and measuring the intensity of one of the new diffraction peaks. The measured diffraction peak intensities were found to reversibly deflect approximately 7% of the reflected light to previously nonexistent peaks. The diffraction grating was formed by patterning a thin film of planar, untreated ITO on a glass substrate using standard photolithography techniques. The size scale for this method of electrically controlled diffraction is limited only by the lithographic process; thus there is potential for the grating to deflect light to angles greater than those achievable using other methods. This approach could be used in applications such as telecommunications, where large deflection angles are required, or other applications where alternate beam-steering methods are cost prohibitive.

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