Applications of neural networks to colour recognition.

Colour specification and matching are important tasks used in a number of different industries. However, current methods can employ very complicated, elaborate pieces of laboratory equipment which are not portable, such as spectrophotometers with combinations of calibrated light sources and a large number of narrow band filters. Simpler, portable devices are typically not sophisticated enough to give a high degree of quality control due to the less sophisticated light sources and the necessarily smaller number of filters employed. Lastly, techniques such as the 'match by eye' method can lead to deceptive metameric matches. This paper outlines the beginning of the development of a colour measurement system which is portable, easy to use, and more accurate than other portable devices by virtue of an artificial neural network used to analyze the data. With specialized training of the neural network, it could even be used in applications such as teeth and skin colour measurements.

Thin-film luminescent concentrators for position-sensitive devices.

The output emittance at the edge of a luminescent concentrator (LC) depends on the physical properties of the dye and matrix used, the spectral intensity of the incident light, and the geometric parameters of the LC. If a projection of the light source on a LC is smaller than its aperture, the LC's output signal will also depend on the position of the projection. This LC feature opens the possibility of determining the position of the light spot and thus building a new type of position-sensitive device. The advantage of LC position-sensitive devices compared with CCD-based sensors is their greater simplicity; LC detection devices have larger linear range than conventional position-sensitive sensors based on discrete photodetectors. Here we describe our study of LC's as two-dimensional position-sensitive elements and analyze, by ray-tracing simulation, different LC designs to get improved linear response. In addition, we discuss experimental results showing real characteristics of position-sensitive devices based on the integration of LC's with photodetectors. We found that spatial resolution of a 12-mm-radius LC-based sensor is of the order of 13 mum within the linear range +/-5 mm.

Modeling a variable-focus liquid-filled optical lens.

Research has been conducted on a variable-focus liquid-filled optical lens built from a polymer elastic-film window and a rigid plastic window with a transparent refractive liquid between these windows. The pressure inside the lens deforms the elastic film, which takes the form of a paraboloid. The absolute value of the tension in the film was calculated, allowing theoretical evaluation of the focal length of the lens and its aberrations. The developed mathematical model of the liquid-filled flexible lens agrees well with experimental results.

Thin-film luminescent concentrators for integrated devices: a cookbook.

A luminescent concentrator (LC) is a nonimaging optical device used for collecting light energy. As a result of its unique properties, a LC also offers the possibility of separating different portions of the spectrum and concentrating them at the same time. Hence, LC's can be applied to a whole range of problems requiring the collection, manipulation, and distribution or measurement of light. Further-more, as described in our previous research, thin-film LC elements can be deposited directly over sensor and processing electronics in the form of integrated LC devices. As an aid to further research, the materials and technology required to fabricate these thin-film LC elements through the use of an ultraviolet-curable photopolymer are documented in detail.