Depth Map Filtering with Adaptive Flying Pixel Thresholds

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Solution Overview

Problem

Existing depth map processing methods using time of flight (ToF) sensors suffer from errors in regions with discontinuous depth, such as object edges, leading to 'flying pixels' with inaccurate depth values, which are not effectively removed by fixed thresholds.

Innovation Solution

A method that determines candidate flying pixels based on confidence level gradients and gradient angles, generates a self-adaptive flying pixel depth threshold using a target pixel's depth value and standard error, and filters these pixels by comparing depth differences in specific reference directions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If fixed thresholds are used for flying pixel removal, then the filtering process is simple, but the accuracy of removing flying pixels is poor

Engineering Contradiction:
Improveaccuracy of flying pixel removalVSAvoidcomplexity of filtering process
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent applies dynamics by transitioning from fixed thresholds to adaptive, dynamically calculated thresholds. The flying pixel determination threshold is no longer a static value but is dynamically adjusted based on local depth map characteristics such as depth gradients and confidence levels at each pixel location. This allows the filtering process to adapt to varying depth discontinuities across different regions of the image, improving accuracy while maintaining computational efficiency through localized adaptive processing.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The patent implements local quality by applying different filtering criteria and threshold values to different regions of the depth map based on local characteristics. Instead of using a uniform threshold across the entire image, the system calculates local depth gradients and confidence levels to determine region-specific thresholds. This enables more accurate identification of flying pixels in areas with high depth discontinuity while preserving valid depth information in homogeneous regions.

Inventive Principle:
Principle #3Local quality

2Measurement precision

If adaptive thresholds are used for flying pixel removal, then the accuracy of removing flying pixels is improved, but the computational complexity increases

Engineering Contradiction:
Improveaccuracy of flying pixel removalVSAvoidcomputational power consumption
Core Design Contradiction:
Measurement precisionVSPower

Solution Approach 1:

The patent applies segmentation by dividing the depth map processing into distinct stages: confidence level calculation, depth gradient computation, threshold determination, and flying pixel identification. Each stage processes specific aspects of the depth data independently, allowing for optimized computational resources at each step. The segmentation also enables parallel processing of different image regions, reducing overall computational power consumption while maintaining adaptive threshold accuracy.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent utilizes parameter changes by modifying threshold values based on local depth map parameters such as depth gradients and confidence levels. Instead of using fixed thresholds, the system dynamically adjusts threshold parameters according to local conditions, achieving high accuracy with efficient computation through parameter-driven adaptive filtering rather than complex algorithms.

Inventive Principle:
Principle #35Parameter changes

3Manufacturing precision

If flying pixels are removed using gradient-based methods, then the precision of depth map filtering is improved, but the processing time increases

Engineering Contradiction:
Improveprecision of depth map filteringVSAvoidprocessing time
Core Design Contradiction:
Manufacturing precisionVSLoss of time

Solution Approach 1:

The patent applies preliminary action by pre-calculating confidence levels and depth gradients for all pixels before performing flying pixel identification. These preliminary computations create ready-to-use parameters that accelerate the main filtering process. By preparing depth gradient maps and confidence level maps in advance, the system reduces the computational burden during the actual flying pixel removal stage, achieving high precision filtering with reduced processing time.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The patent implements skipping by using pre-computed depth gradients and confidence levels to rapidly identify flying pixels without performing complex iterative analysis. The method directly compares local depth differences against adaptive thresholds derived from preliminary calculations, allowing the system to quickly process and filter flying pixels across the entire depth map while maintaining high precision through gradient-based detection.

Inventive Principle:
Principle #21Skipping (Rushing through)

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

Improves the accuracy of depth map filtering by adaptively removing flying pixels, reducing misjudgment and enhancing applications like gesture recognition and three-dimensional modeling.

Implementation Method 1

when measuring a depth of an object based on a time of flight (ToF) sensor, the ToF sensor determines a distance between the sensor and the object by calculating flight time of a pulse signal

Methodology Applied
Scientific EffectTime of flight: Time of Flight

Data Source

PatentEP3979203B1Depth map processing method and apparatus, electronic device and readable storage medium
Publication Date: 2025.07.30 GUANGDONG OPPO MOBILE TELECOMMUNICATIONS CORP LTD
  • EP3979203B1 patent drawingFigure 1~3
  • EP3979203B1 patent drawingFigure 4~5
  • EP3979203B1 patent drawingFigure 6

AI summary

Disclosed are a depth map processing method, a depth map processing apparatus, an electronic device, and a readable storage medium. The method comprises: (101) acquiring a depth map to be processed; (102) acquiring a confidence level gradient and gradient angle of each pixel in the depth map; (103) determining a candidate flying pixel and a target pixel according to the confidence level gradients, and generating a flying pixel depth threshold according to a depth value of the target pixel; (104) acquiring depth values of a pair of pixels adjacent to the candidate flying pixel in a reference direction; and (105) acquiring depth difference values, and determining, according to the depth difference values and the flying pixel depth threshold, whether the candidate flying pixel is a flying pixel.