This optical illusion device is of the type which has a sculpted or relief image-forming surface resembling in shape a negative of the object whose image is to appear when the image-forming surface is viewed. The device is improved to yield a more attractive image by providing altered shading to the negative image-forming surface. The contour of the image forming surface is exposed or unframed to provide a free standing contour. The relief of the image-forming surface is altered to control shadowing when illuminated from a predetermined illumination angle. The substrate on which the image-forming surface is provided is similarly sculpted in detail on an opposite side to provide both a visually appealing sculpture as well as a good image providing surface on the negative, and the substrate is mounted for viewing from either side. The image-forming surface has a main image portion and at least one peripheral image portion with an outer edge of the peripheral portion being shaped to hide the peripheral portion when viewed from an extreme angle at which the image of the peripheral portion should not be part of the image seen. The image-forming negative surface may be translucent, and a surrounding frame member connected to the front edge of the negative surface guides light from the rear onto a rear side of the negative translucent surface while providing a rear mounting surface.

An improved rear projection screen for projecting a three-dimensional head or face is designed to accurately match the apparent movement of a imaged person eyes to movements of an observer, thereby maintaining eye contact between the imaged person and the observer as the observer moves relative to the image. This unique effect called "visualactivity" enables either a recorded or a live image of a person to engage observers with eye contact in a natural and interpersonal way despite movement of the observers relative to the image. This effect is achieved by projecting an image onto the convex side of a rear projection screen that roughly has the shape of a human head and face but is configured with proportions that are different from the natural proportions of the imaged person's face. When viewed from the concave side, this combination produces a realistic human face that appears to turn to accurately track an observer's movements.

A simple method for segmenting eyes and extracting parameters enables further processing of the image to enable a person to appear to be making eye contact with another via a video conferencing system. This method is a first step for eye synthesis and gaze detection because it can automatically extract select eye parameters useful to these processes. Its advantage is that no a priori information is necessary to segment eyes, unlike modeling and neural network methods. The method of the present invention first blurs the image to make it easier to determine the location of the two eye regions in the image. The eyebrows are then eliminated based on the located eye regions. The eyes are then segmented and the eye parameters are extracted from the resulting image According to the present invention, the process applies a Gaussian filter, h(x, y), where g(x, y) is the resulting image and .function.(x, y) is the original image.

Solid phase methods for the identification of an analyte in a biological medium, such as a body fluid, using bioluminescence are provided. A chip designed for performing the method and detecting the bioluminescence is also provided. Methods employing biomineralization for depositing silicon on a matrix support are also provided. A synthetic synapse is also provided.