Light Field Depth Estimation via Epipolar Gradient Analysis

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Solution Overview

Problem

Existing light field capture devices face challenges in rapidly determining depth information from light field images, which is crucial for providing effective visualization tools and user feedback for controlling camera positioning and capturing images.

Innovation Solution

A method that analyzes strong edges in light field images by rearranging data into epipolar images, calculating local gradients, and using gradient orientation to estimate depth, thereby generating a depth map for user interfaces.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If traditional depth determination methods are used on light field images, then depth information can be obtained, but the computational complexity and processing time are excessively high

Engineering Contradiction:
Improvedepth information accuracyVSAvoidprocessing speed
Core Design Contradiction:
Measurement precisionVSProductivity

Solution Approach 1:

The patent segments the light field data into multiple epipolar images (EPIs) by rearranging the 4D light field data into 2D slices. This segmentation allows depth analysis to be performed on individual EPIs rather than the entire 4D dataset, significantly reducing computational complexity while maintaining depth measurement accuracy through gradient analysis on each segmented image.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent extracts only the essential depth-relevant information from the light field data by calculating local gradients on epipolar images. Instead of processing the complete light field dataset, the method extracts gradient magnitude and orientation information from selected EPIs, which contains sufficient depth information while minimizing computational resources required.

Inventive Principle:
Principle #2Taking out (Extraction)

2Reliability

If comprehensive light field data processing is performed to ensure reliable depth information, then measurement reliability improves, but computational resources and processing time increase

Engineering Contradiction:
Improvedepth information reliabilityVSAvoidcomputational energy consumption
Core Design Contradiction:
ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent applies local quality analysis by computing gradients only on specific epipolar images and specific regions within those images where depth information is most reliably present. This localized approach ensures high reliability of depth measurements in critical areas while avoiding unnecessary computational energy consumption in regions where depth information is less significant or already well-determined.

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The patent performs partial action by selecting a subset of epipolar images for gradient analysis rather than processing all possible EPIs. This partial processing approach maintains sufficient depth measurement reliability by focusing on the most informative EPIs while significantly reducing the computational energy required compared to exhaustive processing of the entire light field dataset.

Inventive Principle:
Principle #16Partial or excessive action

Data Source

PatentUS8988317B1Depth determination for light field images
Publication Date: 2015.03.24 GOOGLE LLC
  • US8988317B1 patent drawing
  • US8988317B1 patent drawing
  • US8988317B1 patent drawing

AI summary

Depth information is determined for elements in a light field image, thus allowing for rapid display of visualization tools to communicate such depth information to a user. Depth of strong edges within the light field image is analyzed, providing improved reliability of depth information while reducing or minimizing the amount of computation involved in generating such information. Strong edges can be identified and analyzed by generating epipolar images, or EPIs, from the light field image. Local gradients are determined for pixels in the EPIs. The magnitude of the local gradient is used to determine a confidence as to whether depth can be reliably estimated from the gradient. The orientation of the gradient is used to determine the depth of a corresponding element of the scene. Suitable output is then generated based on the determined depths, for example to provide information and feedback to aid a user in capturing light-field images.