SAR Autofocus via Spatial Phase Error Subpatch Segmentation
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Solution Overview
Problem
Current synthetic aperture radar systems face challenges in producing uniformly focused images due to spatially variant phase errors, which are not adequately addressed by existing autofocus techniques, especially as image resolution increases and terrain elevation changes.
Innovation Solution
A method that identifies a spatial model for phase error variation, divides the image into subpatches based on this model, applies phase correction to each subpatch, and merges them to form a focused image, effectively addressing spatially variant phase errors without requiring extensive terrain data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current autofocus techniques are used to correct phase error, then common phase error can be corrected, but spatially variant phase error varies with target position and cannot be uniformly corrected
Solution Approach 1:
The patent divides the image into multiple subpatches and applies different phase correction parameters to each subpatch. This segmentation allows the system to handle spatially variant phase errors by treating each local region independently with its own correction parameters, thereby resolving the contradiction between correction accuracy and spatial adaptability.
Solution Approach 2:
The patent implements local quality by allowing different phase correction parameters for different spatial locations. Each subpatch receives customized phase correction based on its local characteristics, enabling the system to adapt to spatially variant phase errors while maintaining high correction accuracy in each local region.
2Measurement precision
If image resolution is increased to improve detail, then more phase error variation occurs across the scene, but current techniques cannot correct this spatially variant error
Solution Approach 1:
By segmenting the high-resolution image into subpatches, the patent enables localized phase correction that adapts to the spatially variant phase errors introduced by high resolution. Each subpatch is corrected independently, maintaining focus uniformity across the entire high-resolution scene.
Solution Approach 2:
The patent applies local quality by using position-dependent phase correction parameters that vary across different regions of the high-resolution image. This allows each local area to be optimally corrected for its specific phase characteristics, maintaining uniform focus quality throughout the high-resolution scene.
3Productivity
If terrain elevation data is used to correct phase error, then correction efficiency improves, but the process becomes more difficult and requires additional data
Solution Approach 1:
The patent applies self-service by estimating phase error directly from the SAR image data itself without requiring external terrain elevation data. The system uses the image content to derive phase correction parameters, making the correction process self-sufficient and eliminating the need for additional data sources while maintaining efficiency.
Data Source
AI summary
A method, apparatus, and computer program product is present for focusing an image. A spatial model for spatial variation in phase error is identified for the image. The image is divided into a number of subpatches based on the spatial model. Phase correction is applied to each of the number of subpatches to form a number of focused subpatches. The number of focused subpatches is merged to form a focused image.