Gray Level Control for Optical Projection Systems
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Solution Overview
Problem
Current projector technologies face limitations in utilizing the bandwidth of light modulators effectively, leading to reduced overall brightness and high switching frequency of light sources when attempting to display multiple images, particularly in naked-eye 3D projectors.
Innovation Solution
A gray level control method that divides the total period into unit periods, alternating between maximum and lower brightness levels to integrate the total gray level, with a ratio of at least 60% of unit periods maintaining maximum brightness, reducing the switching frequency of the light source and optimizing light modulator usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If pulse width modulation or pulse amplitude modulation is applied to modulate the brightness of the light source to lower the switching number the light modulator needs, then the switching frequency of the light modulator is reduced, but the overall light brightness is lowered
Solution Approach 1:
The display period is segmented into multiple unit periods, with different numbers of on-states allocated to each. This segmentation allows the system to distribute the gray level formation across time segments, reducing the switching burden on the light modulator while maintaining overall brightness through cumulative light output.
Solution Approach 2:
The patent employs periodic switching patterns within unit periods, where the light modulator switches on and off in regular cycles. By structuring the switching as periodic actions within each unit period, the system reduces peak switching frequency requirements while accumulating sufficient light output over the complete display period.
2Adaptability or versatility
If multiple light sources and time-division multiplexing method are used to output multi-view images, then the number of images displayed is increased, but the switching frequency of the light modulator must be increased which has physical limitations
Solution Approach 1:
The display period is divided into multiple unit periods, with each unit period dedicated to displaying a different view image. This temporal segmentation allows multiple views to be displayed sequentially without requiring the light modulator to switch at excessively high frequencies, accommodating the physical limitations of the device.
Solution Approach 2:
The patent transitions from spatial multiplexing to temporal multiplexing by adding a time dimension to the display process. Instead of attempting to display multiple views simultaneously (spatial approach), the system displays them sequentially in different time slots (temporal approach), effectively using the time dimension to resolve the switching frequency constraint.
3Ease of operation
If the light source rapidly switches to change brightness in accordance with switching time of the light modulator, then the gray level control is achieved, but the light source switching has physical limitations
Solution Approach 1:
The gray level control is achieved by segmenting the display period into unit periods, where the light source brightness is modulated over longer time scales. This segmentation allows gray level control to be implemented without requiring the light source to switch rapidly, as each unit period provides sufficient time for the light source to reach its target brightness level.
Solution Approach 2:
The system performs preliminary brightness adjustment of the light source at the beginning of each unit period, ensuring that the light source reaches the required brightness level before the light modulator needs to switch. This preliminary action approach allows slower light source switching while maintaining precise gray level control.
Data Source
AI summary
The invention provides a gray level control method for outputting a total gray level during a total period, including: dividing the total period into M unit periods; alternatively outputting a gray level “0” or a selected gray level during each unit period; and integrating the gray levels output during the M unit periods to obtain the total gray level, wherein during each of N successive unit periods of the M unit periods the selected gray level is a first gray level, and during each of the remaining (M−N) unit periods the selected gray level is lower than the first gray level.