Calibrating Image Acquisition Devices Using Light Source Patterns
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Solution Overview
Problem
Existing calibration methods for image acquisition devices, particularly light-field capture devices, fail to accurately estimate the chief ray direction and geometrical characteristics of pixel beams due to complex designs and precision issues with microlens arrays, leading to inaccuracies in image processing.
Innovation Solution
A method involving the emission of light source patterns to adjust and analyze the image patterns formed on the sensor, using a two-step approach to iteratively modify the source pattern until it exhibits a centroid aligned with a reference pixel, allowing precise characterization of pixel beams by determining the homomorphic transform and deconvolving the source pattern to estimate the pixel beam's geometric characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional checkerboard or grid calibration patterns are used, then the calibration process is simple to implement, but the measurement precision of chief ray direction and pixel beam characteristics deteriorates
Solution Approach 1:
The patent introduces a light source pattern as an intermediary calibration object that emits structured light through the optical system. This light source pattern serves as a mediator between the calibration target and the sensor, enabling precise measurement of chief ray directions and pixel beam characteristics by analyzing the emitted light patterns rather than relying on passive checkerboard or grid patterns.
Solution Approach 2:
The patent changes the calibration approach from geometric pattern recognition (checkerboards) to optical parameter measurement (light emission patterns). By measuring the spatial and angular distribution of emitted light, the system achieves higher precision in determining chief ray directions and pixel beam characteristics while maintaining calibration simplicity.
2Adaptability or versatility
If microlens arrays are used in light-field capture devices, then the device can capture directional light information, but manufacturing precision issues cause misalignment and calibration inaccuracies
Solution Approach 1:
The calibration method uses the optical system itself (including the microlens array) to generate the calibration pattern by emitting light through the system. This self-service approach eliminates the need for separate high-precision alignment fixtures, as the system's own optical path is used to create the calibration reference, thereby compensating for manufacturing tolerances.
Solution Approach 2:
The patent performs preliminary characterization of the optical system's actual light paths by emitting test patterns and measuring the resulting image patterns before final calibration. This preliminary action captures the actual state of the microlens array including any manufacturing deviations, allowing the calibration to be based on real system behavior rather than idealized specifications.
3Measurement precision
If accurate calibration data is obtained through iterative light pattern adjustment, then image processing accuracy is improved, but the calibration time and complexity increase
Solution Approach 1:
The patent implements an iterative feedback process where light source patterns are emitted, the resulting image patterns are measured, and the light source pattern is adjusted based on the measurement results. This feedback loop continues until convergence, ensuring high precision calibration while providing a systematic approach that can be automated and optimized.
Solution Approach 2:
The calibration process focuses on calibrating specific regions or pixels that require highest precision rather than uniformly calibrating the entire sensor array. By applying calibration efforts selectively to critical areas, the system achieves high measurement precision for important pixels while reducing overall calibration time and computational complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method improves the precision of chief ray position and direction estimation, enabling accurate determination of pixel beam characteristics, even in complex light-field acquisition devices, enhancing the accuracy of image processing and calibration.
Implementation Method 1
emitting at least one light source pattern in an object space of the image acquisition device
Data Source
AI summary
A method of calibrating an image acquisition device is described. The method includes emitting at least one light source pattern in an object space of the image acquisition device, adjusting one of the source patterns until an image pattern of the source pattern formed on a sensor of the image acquisition device exhibit a shape which centroid corresponds to a centroid of a reference pixel of the sensor, called a target image pattern and analyzing the adjusted source pattern and estimating therefrom at least one characteristic of a pixel beam directed to the reference pixel from the adjusted source pattern.