Method of digital grayscale control using modulation of a slow-acting light source

Abstract

A method of digital grayscale control using light source modulation. First, a light valve, grayscale data, and a light source are provided. The light valve includes a spatial light modulator with at least one pixel. The grayscale data indicates desired grayscale level for the pixel during a frame period. The light source is configured to illuminate the pixel, to generate light with increasing intensity for a rise-time after electric power to the light source is substantially increased, and to generate light with decreasing intensity for a decay-time after electric power to the light source is substantially reduced. The light source may be an arc-lamp. The rise-time and the decay-time taken together may constitute a majority of the frame period. During the frame period, the electric power to the light source is substantially increased and is substantially decreased. Substantially decreasing the electric power to the light source may include turning off the electric power. The frame period is divided into at least four time slices with independent durations so that at least one of the at least four time slices occurs completely during the decay time. This may include selecting the at least four independent durations so that a product of each of the at least four independent durations and an average intensity of the light generated by the light source over each of the at least four time slices, respectively, has a binary weighted value, respectively. The pixel is independently set to one of an 0 state and an 1 state during each of the at least four time slices of the frame period based on the grayscale data.