Simple Calibration Algorithm for High-Distortion Lens Camera
IEEE Transactions on Pattern Analysis and Machine Intelligence
Camera Calibration with Distortion Models and Accuracy Evaluation
IEEE Transactions on Pattern Analysis and Machine Intelligence
IEEE Transactions on Very Large Scale Integration (VLSI) Systems - Special issue on the 1995 IEEE ASIC conference
Some Aspects of Zoom Lens Camera Calibration
IEEE Transactions on Pattern Analysis and Machine Intelligence
Invited Address: Integrated Memory/Logic Architecture for Image Processing
VLSID '98 Proceedings of the Eleventh International Conference on VLSI Design: VLSI for Signal Processing
An efficient multiplier-less architecture for 2-D convolution with quadrant symmetric kernels
Integration, the VLSI Journal
A VLSI implementation of barrel distortion correction for wide-angle camera images
IEEE Transactions on Circuits and Systems II: Express Briefs
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Endoscopic images are subjected to spatial distortion due to the wide-angle configuration of the camera lenses. This barrel type of non-linear distortion should be corrected before these images are subjected to further analysis for diagnostic purposes. An efficient digital architecture suitable for an embedded system which can correct the barrel distortion in real-time is presented in this paper. The theoretical approach of this spatial warping technique is based on least-squares estimation. The images in the distorted image space are mapped onto the corrected image space by using a polynomial mapping model. The polynomial parameters include the expansion coefficients, back-mapping coefficients, distortion centre and corrected centre. Several experiments were conducted by applying the spatial warping algorithm on many endoscopic images. A digital architecture suitable for hardware implementation of the distortion correction technique is developed by mapping the algorithmic steps onto a linear array of processing modules. Each module of a particular unit communicates with its nearest neighbours. The spatial warping architecture implemented and simulated with Altera's Quartus II software shows an overall computation time of 1.8 ms with 50 MHz clock for an image of size 256×192 pixels, which confirms that the spatial warping module could be mounted as a dedicated unit in an endoscopy system for real-time applications.