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A simple phase grating is constructed by insertion of a liquid-crystal layer between two glass plates, upon one of which a pair of transparent interdigitated electrodes is formed. With a bias application, liquid-crystal molecules align themselves along the electric field lines, which are substantially parallel to the glass plates. By controlling the degree of this in-plane switching for the liquid-crystal molecules, one can generate various phase-shift distributions for the light passing through the device. The grating characteristics are altered accordingly. Versatile design and ease of fabrication are potential advantages of this device for some future applications.

A luminous reflective display can be constructed by placing an electro-optic shutter on the stack of a luminescent layer, a color filter, and a reflector in this order. The luminescent materials convert a part of the incident light to photoluminescence photons. The reflector redirects the downward photon flux toward an observer. The color filters prevent the photons with unwanted wavelengths from being reflected. The upward spectral flux from this multi-layer structure is formulated. Experiments with off-the-shelf components revealed more than three-fold increase in spectral flux and up to 55% color gamut extension, compared with a control device without luminescent materials.

The principles of fingerprint imaging are based on scattered-light detection, and the technique is proposed for a compact input device. Light enters a glass plate from its edge and propagates inside the plate by repeating the total internal reflection at the boundaries with air. The ridges of a finger pressed onto the plate scatter the light, which then leaks out of the plate. This scattered light is imaged by an array of gradient-index optical fibers and an image sensor. A prototype sensor has been developed: The distance between the finger and the image sensor is 13 mm. The images obtained with this prototype clearly show not only the ridges and valleys but also the pores in the ridges.

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A highly sensitive charge-sensitive amplifier IC was used to read out large-area two-dimensional arrays of amorphous silicon (a-Si) p-i-n photodiodes addressed by a-Si thin film transistors (TFTs). At the highest sensitivity mode, the random noise of the sensor was equivalent to an input charge of 1500 electrons rms. Feedthrough charge injection associated with TFT switching had to be avoided at the expense of the signal charge. Image lag caused by charge trapping in a-Si was suppressed by limiting the input light intensity. A simple model was developed for the noise contribution from a pixel and compared with measurements.

Six inch diagonal, two-dimensional amorphous silicon imaging arrays with 256×240 pixels of 450 micron pitch have been fabricated. Examples of images made under visible light and X-rays illustrate applications to electronic document input and medical imaging. The limits to the array performance are explored through studies of image lag due to deep trapping at dangling bond defects in the a-Si:H sensor, and through measurements of electronic noise.