Scanning Display Mirror Deflection Control for Keystone Distortion
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Solution Overview
Problem
Scanning display systems face challenges in maintaining constant image size and brightness, and correcting for keystone distortion, as these parameters are affected by the distance between the projector and the display surface, as well as the angular extents of mirror deflection.
Innovation Solution
The system dynamically modifies the vertical and horizontal angular extents of the scanning mirror's deflection using actuating circuits and a display size control circuit, which adjusts based on user input, time-of-flight detection, and ambient light levels to maintain constant image size or brightness and correct for keystone distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the distance between the projector and the display surface varies, then the image size changes, but maintaining constant image size requires dynamic adjustment of mirror deflection angular extents
Solution Approach 1:
The patent applies dynamics by making the mirror deflection angular extents dynamically adjustable rather than fixed. The system continuously modifies the vertical and horizontal angular extents of the scanning mirror based on detected distance to the projection surface, allowing the display size to remain constant despite variations in projector-to-screen distance. This dynamic adaptation resolves the contradiction between maintaining image size consistency and avoiding complex control systems.
Solution Approach 2:
The patent implements feedback control by using a distance detection mechanism (such as a time-of-flight sensor or optical feedback system) to measure the distance between the projector and the display surface. This detected distance information is fed back to the control system, which then adjusts the mirror deflection angular extents accordingly. This closed-loop feedback approach enables automatic compensation for distance variations while maintaining relatively simple system architecture.
2Illumination intensity
If the ambient light level changes, then the perceived brightness changes, but maintaining constant brightness requires dynamic modification of display parameters
Solution Approach 1:
The patent employs ambient light sensing feedback to detect changes in environmental lighting conditions. The control circuit receives information about ambient light levels and dynamically adjusts display parameters (such as laser power or mirror deflection characteristics) to compensate for brightness variations. This feedback mechanism maintains consistent perceived brightness across varying ambient light conditions while keeping the control circuit design manageable.
Solution Approach 2:
The patent applies parameter changes by modifying display system parameters (such as laser output power or scanning angular extents) in response to detected ambient light level changes. When ambient light increases, the system adjusts parameters to maintain constant perceived brightness, and vice versa. This dynamic parameter adjustment resolves the contradiction between brightness consistency and control circuit complexity.
3Length of moving object
If the angular extents of mirror deflection are increased to maintain image size at closer distances, then the scanning speed increases, but image brightness may decrease due to reduced dwell time per pixel
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting multiple parameters in coordination: when the mirror deflection angular extents are increased to maintain image size at closer distances, the system simultaneously adjusts the laser power or pulse duration to compensate for the reduced dwell time per pixel. This coordinated parameter adjustment ensures that both image size and brightness remain constant despite changes in scanning angular extents.
Solution Approach 2:
The patent utilizes periodic action by adjusting the laser pulse timing and duration to match the modified scanning period. When angular extents change, the system synchronizes the laser emission characteristics with the new scanning rhythm, ensuring that each pixel receives appropriate light exposure despite variations in scan speed. This periodic coordination maintains brightness consistency while adapting to different image size requirements.
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 ensures that the image size and brightness remain consistent across varying distances and corrects for keystone distortion, providing a stable and high-quality display experience.
Implementation Method 1
time-of-flight detection
Data Source
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AI summary
A scanning projector includes a MEMS device (160) with a scanning mirror (162) that sweeps a beam in two dimensions. Actuating circuits receive scan angle information and provide signal stimulus to the MEMS device to control the amount of mirror deflection on two axes. The scan angle information may be modified to maintain a constant image size, a constant image brightness, and/or to correct for keystone distortion.