Shift Correction Parameter for 4D Light Field Aberration

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Solution Overview

Problem

4D light field data acquisition devices, such as plenoptic cameras, suffer from optical aberrations in their main lenses, which degrade the quality of acquired images and existing correction methods require precise knowledge of the lens geometry.

Innovation Solution

A method that determines a shift correction parameter using a test-chart image with contrasted details, allowing for pixel-level shift estimation between sub-aperture images without needing sharp knowledge of the main lens geometry, and applies this parameter to refocused images to correct for aberrations like spherical and chromatic aberrations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If ray tracing technique with precise knowledge of lens geometry is used to correct optical aberrations, then correction accuracy is improved, but device complexity and manufacturing requirements increase

Engineering Contradiction:

Improvecorrection accuracyVSAvoidlens geometry knowledge requirement

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent creates a virtual model of the light field by capturing images through multiple virtual cameras positioned at different locations. This virtual copy of the optical system allows aberration correction through computational methods rather than requiring precise physical measurements of the actual lens geometry, thereby reducing manufacturing complexity while maintaining correction accuracy

Inventive Principle:

Principle #26Copying

Solution Approach 2:

The patent replaces the mechanical/optical approach of precisely manufacturing and measuring lens geometry with a computational approach using virtual camera models and ray tracing algorithms. This substitution of computational methods for physical measurements reduces the need for precise lens geometry knowledge and specialized manufacturing equipment

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Manufacturing precision

If multiple sub-aperture images are processed with shift correction to reduce optical aberrations, then image quality is improved, but processing time and computational resources increase

Engineering Contradiction:

Improveimage qualityVSAvoidprocessing time

Core Design Contradiction:

Manufacturing precisionVSLoss of time

Solution Approach 1:

The patent pre-calculates and stores shift correction parameters for multiple sub-aperture images during an initial processing stage. These pre-computed parameters are then applied efficiently during the actual image reconstruction phase, reducing the computational burden and processing time when generating the final corrected image while still achieving high image quality

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent divides the correction process into separate stages: first processing individual sub-aperture images to determine shift parameters, then combining these corrected sub-images to form the final refocused image. This segmentation allows parallel processing of different sub-aperture images and optimizes computational resource utilization, reducing overall processing time while maintaining correction effectiveness

Inventive Principle:

Principle #1Segmentation

3Reliability

If shift correction parameter is determined from test-chart image to correct lens aberrations, then correction effectiveness is improved, but measurement and calibration complexity increase

Engineering Contradiction:

Improvecorrection effectivenessVSAvoidtest-chart analysis complexity

Core Design Contradiction:

ReliabilityVSDifficulty of detecting and measuring

Solution Approach 1:

The patent uses a test chart with distinct color patterns and high contrast features that make it easy to detect and measure positional shifts between sub-aperture images. The specific color choices and patterns are designed to maximize contrast and facilitate automated detection algorithms, reducing the complexity of measurement while improving the reliability of shift parameter determination

Inventive Principle:

Principle #32Color changes

Solution Approach 2:

The test chart is designed with self-referential features where patterns repeat at known intervals and positions. This allows the system to automatically detect and correct shifts by comparing corresponding patterns across sub-aperture images without requiring external reference measurements or complex calibration procedures, thereby improving correction effectiveness while reducing measurement complexity

Inventive Principle:

Principle #25Self-service

Data Source

PatentUS10334229B2Method for obtaining a refocused image from a 4D raw light field data using a shift correction parameter

Publication Date: 2019.06.25 INTERDIGITAL CE PATENT HOLDINGS SAS

AI summary

A method for obtaining a refocused image from a 4D raw light field data for a given focus (zfocus) is described. The method is remarkable in that it comprises applying a shift correction parameter on shifted and summed images from said 4D raw light field data, the shifted and summed images being defined as a function of the given focus (zfocus), and the shift correction parameter (Δ) including, for at least a part of pixels of at least two sub-aperture images derived from at least one 4D light field data of a test-chart image, determined shifts for pixels belonging to the part of pixels between the at least two sub-aperture images, the test-chart image comprising patterns adequate to compute disparities between the sub-apertures images.