Object detection is an important task in computer vision and is widely used in applications ranging from autonomous driving to industrial safety, where it enables automatic monitoring of personal protective equipment compliance and improves workplace safety. Models like YOLO11 perform very well on clear, high-quality images, but their performance decreases when the images are degraded. The goal of this thesis is to examine how different types of image degradation affect the YOLO11 model and to determine the points at which object detection becomes unreliable.
The theoretical part explains the fundamentals of object detection, the YOLO11 model, and the main evaluation metrics, including precision, recall, Intersection over Union (IoU), F1-score, and mean Average Precision (mAP). A custom dataset with seven classes was created: five object classes (helmet, gloves, safety footwear, safety vest, person) and two classes representing safety violations (without helmet and without gloves). This setup allows not only the detection of protective equipment but also the direct identification of safety rule violations.
The YOLO11 model was trained on clean images and tested on both clean and artificially degraded images. The model’s performance on clean images was evaluated using precision, recall, F1 score, and mAP, while the impact of five types of image degradation: Gaussian white noise, impulse noise, motion blur, JPEG compression and changes in brightness and contrast was analysed using the average confidence of detections. On clean images, the model achieved an mAP@0.5 of 0.955, an F1 score of 0.92, and an average confidence score of 0.63. The results showed that impulse noise had the strongest negative effect and could completely prevent the model from detecting objects at higher levels. Motion blur also reduced performance significantly, while Gaussian white noise caused a gradual decrease in detection confidence. JPEG compression had the smallest impact, changes in brightness and contrast only slightly affected the results.
The results show that the YOLO11 model is suitable for automatically monitoring the use of personal protective equipment in industrial environments. This thesis also improves understanding of how image quality affects object detection and highlights the importance of proper image preprocessing for reliable performance in real-world situations.
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