Image Converter Cylindrical Projection Fisheye Distortion
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Solution Overview
Problem
Conventional image converters fail to produce distortion-free planar regular images from distorted circular images captured with fisheye lenses, especially in security camera applications, where detailed features need to be recognized, and existing methods either distort images further or restrict the region that can be cut out, leading to blind spots.
Innovation Solution
An image converter that maps pixels from a distorted circular image on a 2D XY orthogonal coordinate system to a 2D UV curved coordinate system, allowing for the extraction of any desired part of the image with reduced distortion by using correspondence relationship equations and a virtual cylindrical column to correct for distortion, enabling smooth panning and improved feature recognition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional image conversion techniques are used to obtain a rectangular planar regular image from a distorted circular image, then the image can be converted to a planar format, but the resulting image is greatly distorted at external parts (contour areas) and inadequate for recognizing detailed features
Solution Approach 1:
The patent applies a cylindrical projection model where the distorted circular image is mapped onto a cylindrical surface rather than a flat plane. This curvature-based approach preserves the geometric relationships in the peripheral regions of the image, eliminating the severe distortion that occurs at the contours when using conventional rectangular projection methods. The cylindrical coordinate system (u, v) is introduced to represent points on the curved surface, allowing accurate representation of spatial relationships throughout the entire image including edge regions.
2Ease of operation
If a panoramic image is provided by converting the distorted circular image to a cylindrical face development, then horizontal panning can be conducted smoothly, but the image is greatly distorted in the perpendicular direction and restriction is imposed on the cut-out region
Solution Approach 1:
The patent introduces a dynamic parameter ω (omega) that controls the degree of curvature application in the image conversion. By adjusting this parameter, the system can dynamically switch between different projection modes: when ω=0, the conversion produces a flat planar image; when ω>0, it applies cylindrical projection with adjustable curvature. This dynamic parameter allows the system to optimize for either smooth panning (higher ω) or maximum cut-out flexibility (lower ω), providing adaptability for different application requirements.
3Ease of operation
If the vicinity of the top is cut out from the distorted circular image to obtain a planar regular image, then the image can be displayed on a monitoring screen, but the cut-out region is greatly distorted and it is actually impossible to cut out the vicinity of the top
Solution Approach 1:
By mapping the image onto a cylindrical surface before extraction, the patent preserves the geometric integrity of regions that would otherwise be severely distorted in conventional flat projections. The vicinity of the top (and all other regions) can now be cut out from the cylindrical representation without experiencing the extreme distortion that occurs when attempting to flatten spherical or circular images directly. This allows monitoring screens to display any desired region with acceptable distortion levels.
4Adaptability or versatility
If a fisheye lens is used to obtain hemispherical circular images in all directions, then the field angle is maximized without mechanical moving mechanisms, but the images are distorted in circular format and not suitable for general photographic uses requiring planar regular images
Solution Approach 1:
The patent transitions the image representation from a two-dimensional flat plane to a three-dimensional cylindrical surface. By introducing the vertical dimension (v-coordinate) that wraps around the cylinder, the system can accommodate the full 360-degree horizontal field of view of the fisheye lens while maintaining regular geometric relationships. This dimensional transformation allows the image to retain the wide angular coverage of fisheye photography while achieving the planar regularity needed for general photographic applications.
Data Source
AI summary
An image converter for performing processes of cutting out a part of a distorted circular image photographed by use of a fisheye lens and converting the part into a planar regular image. The image converter includes a distorted circular image memory, a planar regular image memory, a parameter input unit, a corresponding coordinate calculating unit, and a planar regular image forming unit.