Projection-Type Display Optical Path Shifting for Flicker Reduction
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Solution Overview
Problem
Flickering occurs in projection-type display apparatus due to alignment defects caused by adjacent liquid crystal elements applying high and low voltages, leading to differences in gray scale levels.
Innovation Solution
A projection-type display apparatus with a liquid crystal panel and optical path shift element that shifts pixel positions every k unit periods, controlled by a display control circuit to adjust gray scale levels and correct pixel data to reduce luminance differences between adjacent pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If panel pixels applying high voltage and low voltage are arranged adjacent to each other in one unit period, then gray scale levels can be expressed, but flickering occurs due to alignment defect
Solution Approach 1:
The frame period is divided into multiple unit periods, and the projection position is shifted for each unit period. This segmentation allows adjacent pixels with different gray scale levels to be separated in the projection direction, preventing alignment defects while maintaining gray scale expression capability
Solution Approach 2:
The patent introduces a temporal dimension by shifting projection positions across different unit periods. Instead of arranging different gray scale pixels side-by-side in space (which causes alignment defects), the same pixel's different gray scale states are displayed at different positions and times, eliminating the harmful spatial adjacency
2Reliability
If optical path shift element shifts projection pixel position for each unit period, then alignment defects are reduced, but device complexity increases
Solution Approach 1:
An optical path shift element is introduced as an intermediary component between the liquid crystal panel and the projection lens. This element shifts the projection position of pixels without requiring complex mechanical movement of the entire projection system, thereby reducing alignment defects while controlling device complexity
Solution Approach 2:
The optical path shift element operates periodically, shifting projection positions at specific intervals (every k unit periods). This periodic operation achieves the necessary position variations to prevent alignment defects while minimizing the operational complexity of the shift mechanism
3Reliability
If gray scale level correction is applied to adjacent pixels, then luminance difference is reduced, but data processing complexity increases
Solution Approach 1:
The display control circuit performs preliminary correction of pixel data before the pixels are displayed. By adjusting the gray scale levels of adjacent pixels in advance based on their spatial relationship and expected luminance differences, the system prevents excessive luminance contrast without requiring complex real-time processing during display
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Reduces flickering and improves display quality by minimizing alignment defects and luminance differences between adjacent pixels through controlled pixel position shifting and data correction.
Implementation Method 1
an optical path shift element configured to shift a position of a projection pixel
Implementation Method 2
an optical path shift element configured to shift a position of a projection pixel
Implementation Method 3
panel pixels respectively applying high voltage and low voltage to liquid crystal elements
Data Source
AI summary
A projection-type display apparatus includes a liquid crystal panel, an optical path shift element, and a display control circuit that controls the liquid crystal panel and the optical path shift element. When a difference in gray scale level between pixel data corresponding to a panel pixel p11 and pixel data corresponding to a panel pixel p12, the panel pixel p11 and the panel pixel p12 being two adjacent pixels, is equal to or larger than a threshold in a unit period 1-2 for example, the display control circuit corrects at least one of a gray scale level of a video pixel corresponding to the panel pixel p12 in a previous unit period 1-1 or a gray scale level of a video pixel corresponding to the panel pixel p11 in a unit period 2-1 to reduce a difference in luminance between the panel pixels.