Keystone Correction Using Separable 1D Operations and Polyphase Filtering
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing keystone correction methods face challenges in ensuring accurate distortion correction, particularly with fixed pixel imagers, as they struggle with illumination uniformity and variable anti-alias filtering requirements, and often result in significant memory bandwidth issues and difficulty in generating new information for all output pixels.
Innovation Solution
The proposed solution involves an image projection system that applies inverse optical distortion using separate 1D processes for horizontal and vertical scaling, incorporating a polyphase filter and pixel accumulation to ensure accurate mapping and uniform brightness, while assuming finite pixel size to address the limitations of interpolation-based methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If forward address mapping approach is used for keystone correction, then memory bandwidth requirements are reduced compared to reverse mapping, but significant difficulty exists in ensuring that new information is generated for all output pixels
Solution Approach 1:
The patent applies a pre-filtering step before the forward address mapping process. This preliminary action prepares the input image data by applying anti-aliasing filters and generating appropriate weighting factors that will be used during the mapping process, ensuring that all output pixels receive valid information while maintaining memory efficiency.
Solution Approach 2:
The patent introduces intermediate weighting factors as a mediator between the input and output images. These weighting factors are calculated based on the mapping relationship and are used to combine multiple input pixels when generating output pixels, ensuring information completeness while working within the constraints of forward mapping.
2Adaptability or versatility
If interpolation-based mapping algorithms are used for optical distortion correction, then image warping can be performed, but illumination uniformity and variable anti-alias filtering requirements are not addressed
Solution Approach 1:
The patent applies different filtering and weighting strategies to different regions of the image based on local requirements. The weighting factors are calculated specifically for each output pixel location, allowing the system to address illumination uniformity and anti-aliasing needs locally while maintaining the overall warping transformation.
Solution Approach 2:
The patent dynamically adjusts filtering parameters and weighting factors based on the local mapping geometry and illumination requirements. By changing these parameters adaptively across different image regions, the system achieves both warping capability and illumination uniformity.
3Adaptability or versatility
If keystone correction is applied to project images at angles, then presenter flexibility is improved, but the projected image becomes distorted requiring correction algorithms
Solution Approach 1:
The patent applies inverse mapping by calculating the transformation from the desired output image coordinates back to the input image coordinates. This inversion approach allows the system to pre-calculate appropriate sampling points and weighting factors, ensuring geometric accuracy while enabling flexible projection angles.
Data Source
AI summary
Methods for reducing optical distortion such as keystone distortion can include receiving an input image and modifying the input image by applying two separate 1D operations to the input image and applying a polyphase filter to the input image, where the first 1D operation is performed after application of the second 1D operation has begun. The modified image can then be projected.