Projector Drive Synchronization to Cancel Horizontal Streaks

The patent applies periodic action by inverting the polarity of the drive voltage at a frequency that matches or exceeds the flicker fusion threshold of human vision. This periodic polarity inversion causes the light modulation device to alternately display positive and negative field images, which when combined, cancel out the horizontal-striped unevenness caused by light source luminance variations. The periodic switching at high frequency creates the perception of uniform brightness while actually displaying alternating polarity patterns.

The patent changes the parameter of drive voltage polarity from static to dynamically alternating between positive and negative values. By varying the polarity parameter at a specific frequency range (above the human visual flicker fusion threshold), the system transforms the static brightness uniformity problem into a dynamic cancellation effect, where the alternating polarity patterns cancel out the horizontal stripes in the human visual system.

The patent uses periodic action by switching the polarity at a frequency specifically chosen to be above the human visual system's flicker fusion threshold. This ensures that the periodic polarity inversion occurs too rapidly for the human eye to detect as separate frames, thereby eliminating visible flicker while maintaining the brightness uniformity benefits.

The patent maintains continuous useful action by ensuring that the polarity inversion frequency is high enough to create the perception of continuous, stable light output. The rapid alternating display of positive and negative fields creates a fused perceptual image that appears continuous and stable, preventing flicker while maintaining the uniformity benefits of polarity inversion.

The patent extracts the complexity of image processing by eliminating the need for post-synchronization picture signal processing. Instead of analyzing and correcting horizontal stripes through complex image processing algorithms, the invention directly addresses the root cause by controlling the polarity inversion timing of the light modulation device, thereby simplifying the overall control system.

The patent applies preliminary action by pre-synchronizing the polarity inversion timing with the vertical synchronizing signal before the picture signal is processed. This preliminary synchronization of the drive voltage polarity with the vertical sync signal prevents horizontal-striped unevenness from occurring in the first place, eliminating the need for subsequent complex image processing corrections.

The patent extracts and eliminates the need for complex picture signal luminance adjustment processing by directly controlling the polarity inversion timing. Instead of processing the picture signal to reduce luminance in specific pulse periods, the invention synchronizes the polarity inversion with the vertical synchronizing signal, thereby preventing horizontal-shaped noise through simple timing synchronization rather than complex image processing.

The patent applies preliminary action by pre-synchronizing the polarity inversion timing with the vertical synchronizing signal before picture signal processing occurs. This preliminary timing synchronization prevents horizontal-shaped noise from generating in the first place, eliminating the need for subsequent luminance reduction processing and simplifying the overall system.