DLP Edge Blend Artefact Reduction via Dithering
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Solution Overview
Problem
In multiple-projector displays, the overlapping of patterning effects in the blend zone leads to noticeable visual artefacts, particularly irregular banding patterns of increased and decreased light intensity, especially with solid colors during eye saccades.
Innovation Solution
A method is introduced to reduce visual artefacts by determining a maximum intensity variance for each pixel group within the blend zone, adjusting the blend multiplier to create first and second adjusted multipliers, and applying these to each pixel group to maintain an average pixel intensity equal to the net light intensity, while introducing spatial intensity variance through dithering to minimize patterning effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electronic edge blending is used in multiple-projector displays, then seamless image transition is achieved, but visual artefacts appear in the blend zone
Solution Approach 1:
The patent modifies the pulse width modulation parameters by introducing dithering patterns that vary the on/off timing of pixel mirrors. This changes the temporal distribution of light output while maintaining the same average intensity, thereby reducing the visibility of patterning effects in the blend zone during eye saccades
Solution Approach 2:
The patent applies periodic dithering patterns to the pixel mirror activation sequences. By introducing controlled periodic variations in the pulse sequences, the patterning effects are distributed over time in a way that reduces their visual impact during rapid eye movements
2Illumination intensity
If pixel mirrors are rapidly repositioned using PWM to achieve intermediate intensity, then light intensity control is improved, but patterning effects occur in solid color regions
Solution Approach 1:
The patent introduces dithering patterns that modify the temporal parameters of pixel mirror actuation. By varying the timing and duration of on/off states within the PWM cycle, the patent maintains the desired average light intensity while distributing the patterning effects across multiple temporal patterns that are less visually apparent
Solution Approach 2:
The patent introduces dithering patterns as an intermediary layer between the desired image intensity and the actual pixel mirror actuation. These patterns act as a mediator that transforms the direct PWM control into a more visually acceptable output by adding controlled temporal variations
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
This approach effectively reduces visual artefacts in the blend zone by maintaining the average pixel intensity and minimizing patterning effects, ensuring a seamless and artifact-free projection, especially in areas prone to such artefacts like solid color backgrounds.
Implementation Method 1
DLP projectors use one or more digital micromirror devices (DMD) to reflect light and produce a picture
Implementation Method 2
using pulse-width modulation (PWM), each pixel mirror is capable of producing various levels of light intensity
Data Source
AI summary
A method of reducing visual artefacts in a blend zone of at least two projector images is provided. The method comprises determining a maximum intensity variance for each pixel group within a blend curve of the blend zone, the maximum intensity variance being based on a blend multiplier selected to achieve a net light intensity specific to the location of the pixel group within the blend curve. For each pixel group, a first adjusted blend multiplier is determined, wherein the blend multiplier is increased by at least a portion of the maximum intensity variance. For each pixel group, a second adjusted blend multiplier is also determined, wherein the blend multiplier is decreased by at least a portion of the maximum intensity variance. The light intensity of each pixel in each pixel group is adjusted using the first and second adjusted blend multipliers specific to each pixel group. The average pixel intensity of each pixel group after application of the first and second adjusted blend multipliers remains equal to the net light intensity of the pixel group within the blend curve.