Dual-Modulator Projector Brightness Control
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Solution Overview
Problem
Projectors face challenges in representing low grayscale values and minimizing background brightness, leading to undesirable artifacts and shimmer, especially when multiple projectors are used to create a large overall image, as existing dithering techniques are inadequate and generate unwanted brightness deviations.
Innovation Solution
A projector system with two modulators and a control unit that independently switches pixels between states to modulate light, allowing for precise brightness adjustment and residual light modulation, enabling the representation of low grayscale values without dithering and reducing shimmer by using pulse-width-modulated control data and boosting techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If dithering techniques (temporal or spatial) are used to represent low grayscale values, then background brightness is minimized, but image quality deteriorates due to shimmer and inability to represent low grayscale values distinguishably
Solution Approach 1:
The invention divides the modulation task into two independent stages using two separate modulators (first modulator with first pixels and second modulator with second pixels). Each modulator independently modulates light for a portion of the frame duration, allowing precise control of low grayscale values without dithering artifacts. This segmentation enables accurate representation of low brightness levels while maintaining minimal background brightness.
Solution Approach 2:
The first modulator performs preliminary light modulation for a first portion of the frame duration, and the second modulator performs subsequent modulation for a second portion. This preliminary action sequence allows the system to establish baseline brightness control before fine-tuning low grayscale values, eliminating the need for dithering techniques that cause shimmer.
2Area of stationary object
If multiple projectors are used to project large images with overlapping edge regions, then image coverage is improved, but brightness accuracy deteriorates due to excessive brightness in low grayscale value regions
Solution Approach 1:
By segmenting the modulation process across two modulators operating at different time portions, the invention enables precise brightness control in edge regions where multiple projector images overlap. This allows accurate representation of low grayscale values in overlap regions without the brightness exaggeration that occurs with conventional single-modulator approaches.
Solution Approach 2:
The control unit coordinates both modulators based on image data, implementing feedback control to maintain accurate brightness levels in overlapping edge regions. The system adjusts modulation depth and timing to compensate for brightness accumulation from multiple projectors, ensuring consistent grayscale value representation across the entire projected image area.
3Device complexity
If conventional single-modulator approaches are used, then device complexity is low, but image quality deteriorates due to unavoidable background brightness and dithering artifacts
Solution Approach 1:
The invention uses two modulators operating at different time portions to segment the brightness control function. This segmentation enables precise control of low grayscale values without dithering, achieving superior image quality despite increased device complexity. Each modulator handles a specific time portion, allowing independent optimization of modulation depth and timing.
Solution Approach 2:
The control unit drives the modulators using periodic action with pulse-width modulation, where each modulator operates during specific time portions of the frame duration. This periodic control scheme enables accurate representation of low grayscale values by precisely controlling the duty cycle of each modulator, eliminating the need for dithering techniques.
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
The system effectively represents low grayscale values with reduced brightness deviations and shimmer, providing a more accurate and seamless image projection, especially in multi-projector setups, by finely resolving the brightness range and compensating for variations in projector settings and image overlap.
Implementation Method 1
The first and second pixels are switchable independently of one another in each case into a first state, in which light incident on them is used for image generation, and into a second state, in which light incident on them does not serve for image generation, in order pixel-individually to modulate the light for generating the image
Implementation Method 2
an imaging optical unit, which images the first modulator onto the second modulator
Implementation Method 3
a projection optical unit, which images light coming from the second modulator onto a projection surface in order to project the image
Data Source
AI summary
The control unit of a projector drives modulators for the range of brightness of the image data with a first resolution of NN levels, wherein NN is an integer greater than one. The control unit applies a predefined brightness change to the brightness value in accordance with the image data for the image point such that a changed brightness value having a second resolution, which is greater than the first resolution, is calculated, and converts the changed brightness value into the increased brightness value such that it has the first resolution and is greater than a notional comparison value having the first resolution that arises if the predefined brightness change is applied to the brightness value in accordance with the image data, with the result that the control unit drives one of the modulators for a pixel to be boosted with the increased brightness value having the first resolution.