Edge-Aware Loss Function for Small-Object Pixel Classification

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Solution Overview

Problem

Existing semantic segmentation methods using convolutional neural networks (CNNs) fail to accurately classify small objects and object boundaries due to the uniform weighting of all pixels in the loss function, leading to erroneous classifications in live in-vehicle systems.

Innovation Solution

A method that incorporates an edge detection algorithm, such as a modified Sobel operator with additional rotated kernels and a bivariate Gaussian kernel, to enhance the contribution of small objects and object boundaries in the loss function by applying it to both predicted segmentation maps and ground truth labels, ensuring accurate classification.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If mean value loss function is used for training, then training simplicity is improved, but classification accuracy for small objects and boundaries deteriorates

Engineering Contradiction:
Improvetraining simplicityVSAvoidclassification accuracy
Core Design Contradiction:
Ease of manufactureVSMeasurement precision

Solution Approach 1:

The patent applies local quality by differentiating the loss function treatment for different regions of the image. Boundary pixels and pixels from small objects are identified and assigned higher weights in the loss function, while other pixels use standard weighting. This allows the training process to focus computational attention on critical regions that require higher classification accuracy, resolving the contradiction between training simplicity and classification accuracy for small objects and boundaries.

Inventive Principle:
Principle #3Local quality

2Productivity

If uniform pixel weighting is used in loss function, then computational efficiency is improved, but reliability of segmentation for critical regions deteriorates

Engineering Contradiction:
Improvecomputational efficiencyVSAvoidsegmentation reliability
Core Design Contradiction:
ProductivityVSReliability

Solution Approach 1:

The patent changes the parameter weighting in the loss function dynamically based on pixel characteristics. Instead of uniform weighting, the loss function incorporates adaptive weights that increase for boundary pixels and pixels belonging to small objects. This parameter change maintains computational efficiency while significantly improving segmentation reliability for critical regions by making the loss landscape more sensitive to errors in important areas.

Inventive Principle:
Principle #35Parameter changes

3Speed

If standard CNN training is used, then processing speed is improved, but detection precision for object boundaries deteriorates

Engineering Contradiction:
Improveprocessing speedVSAvoidboundary detection precision
Core Design Contradiction:
SpeedVSMeasurement precision

Solution Approach 1:

The patent applies preliminary action by pre-identifying boundary pixels and small object pixels before the main training process. These critical pixels are marked and assigned special weights in advance, allowing the standard CNN training algorithm to proceed at high speed while automatically focusing on the right regions. This preliminary classification enables the model to achieve high boundary detection precision without sacrificing processing speed, as the weighted loss function guides learning toward critical regions during normal training operations.

Inventive Principle:
Principle #10Preliminary action

Data Source

PatentEP4036792B1Method and device for classifying pixels of an image
Publication Date: 2025.10.22 APTIV TECHNOLOGIES AG
  • EP4036792B1 patent drawingFigure 1
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AI summary

A method is provided for classifying pixels of an image. An image comprising a plurality of pixels is captured by a sensor device. A neural network is used for estimating probability values for each pixel, each probability value indicating the probability for the respective pixel being associated with one of a plurality of predetermined classes. One of the classes is assigned to each pixel of the image based on the respective probability values in order to create a predicted segmentation map. For training the neural network, a loss function is generated by relating the predicted segmentation map to ground truth labels. Furthermore, an edge detection algorithm is applied to at least one of the predicted segmentation map and the ground truth labels, wherein the edge detection algorithm predicts boundaries between objects. Generating the loss function is based on a result of the edge detection algorithm.