Sub-pixel Displacement Detection via Image Interpolation
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Solution Overview
Problem
Conventional methods for detecting sub-pixel displacement are limited by errors introduced when displacements become larger and are sensitive to noise, unable to accurately determine tiny movements smaller than one pixel width, and have restricted searching capabilities.
Innovation Solution
A method and apparatus using an optical navigation device with an image capturing unit, interpolation unit, and processing unit that captures array images, interpolates them to form reference and comparison images, and performs a two-stage searching process to calculate sub-pixel accurate displacement, increasing the searching area and resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the first order Taylor Expansion equations are used for detecting sub-pixel displacement, then the detection method is simple and suitable for small displacements, but errors are introduced when displacements become larger and the method is sensitive to noise
Solution Approach 1:
The patent applies preliminary action by performing interpolation on the captured images before conducting displacement detection. The interpolation unit generates intermediate pixel values between actual pixels, creating an enhanced image representation that allows for more accurate displacement measurement. This preliminary image enhancement enables the system to achieve sub-pixel accuracy without relying on approximate mathematical models, thereby resolving the contradiction between simplicity and accuracy.
2Productivity
If conventional correlation methods are used with pixel-level resolution, then the searching area is limited to integer pixel positions, but tiny movements smaller than one pixel width cannot be determined
Solution Approach 1:
The patent changes the parameter of image resolution by introducing interpolation that generates sub-pixel positioned virtual pixels. This transforms the discrete pixel grid into a continuous coordinate system where displacement can be measured at fractional pixel levels. The interpolation unit calculates intensity values at non-integer positions, enabling the system to detect movements smaller than one pixel width while maintaining searching efficiency through the structured interpolation approach.
Data Source
AI summary
A method of detecting displacement with sub-pixel accuracy includes the steps of: capturing a first array image and a second array image; interpolating the first array image to form a reference image; interpolating the second array image to form a comparison image; comparing the reference image with the comparison image so as to obtain a displacement. The present invention also provides an apparatus for detecting displacement with sub-pixel accuracy.