All You Need is LUV: Unsupervised Collection of Labeled Images using Invisible UV Fluorescent Indicators

Brijen Thananjeyan*, Justin Kerr*, Huang Huang, Joseph E. Gonzalez, Ken Goldberg

UC Berkeley AUTOLab

*denotes equal contribution

Summary

LUV allows anyone to quickly and easily generate high-quality labelled training images to train neural network to reliably recognize features such as thin thread, thin needles, fabric corners, plastic bag handles. This site provides a shopping list for around 300$ of off-the-shelf parts; after setup data collection is runnable on any standard Linux machine on the same local network as the smart plugs. 


UV light is only used during data collection, after which the trained networks (any standard segmentation network like U-Net, FCN, etc) can be used on unmarked objects.

Shopping List

Hardware

Paints

We recommend starting with the lacquer based paint and markers, and seeing how well they fit your needs. 

Abstract

Large-scale semantic image annotation is a significant challenge for learning-based perception systems in robotics. Current approaches often rely on human labelers, which can be expensive, or simulation data, which can visually or physically differ from real data. This paper proposes Labels from UltraViolet (LUV), a novel framework that enables rapid, labeled data collection in real manipulation environments without human labeling. LUV uses transparent, ultraviolet-fluorescent paint with programmable ultraviolet LEDs to collect paired images of a scene in standard lighting and UV lighting to autonomously extract segmentation masks and keypoints via color segmentation. We apply LUV to a suite of diverse robot perception tasks to evaluate its labeling quality, flexibility, and data collection rate. Results suggest that LUV is 180-2500 times faster than a human labeler across the tasks. We show that LUV provides labels consistent with human annotations on unpainted test images. The networks trained on these labels are used to smooth and fold crumpled towels with 83% success rate and achieve 1.7mm position error with respect to human labels on a surgical needle pose estimation task. The low cost of LUV makes it ideal as a lightweight replacement for human labeling systems, with the one-time setup costs at $300 equivalent to the cost of collecting around 200 semantic segmentation labels on Amazon Mechanical Turk.

Transparent Markings with UV-Fluorescent Paint

LUV relies on paint that is nearly transparent under visible light, but fluoresces under ultraviolet radiation. We leverage this property by painting relevant objects and keypoints. For example, in a cable segmentation perception task, we paint the entire cable with UV-fluorescent paint. In a towel corner detection task, we paint the corners of each towel with UV-fluorescent paint.



Human-Free Annotations for Real Images

First, an image is taken of the workspace. To generate masks, the UV lights are turned on, and if available the ambient white lights turned off. The camera exposure for each sample is found by manually sweeping exposures and selecting the exposure yielding clearest label colors. For scenes with both dark and light painted materials, multiple exposures can be captured and post-processed with HDR to retrieve well exposed labels for all colors. We perform HSV color filtering on the UV images to extract the training labels.

Training and Execution Time

We then train a perception network on the labeled training dataset to predict keypoints and segmentation masks. During execution, no UV labels or painted objects are required, and we evaluate the trained network on standard images of the workspace. On the left, we present evaluations of the trained networks on unseen test images for three tasks: towel corner detection, cable segmentation, and needle segmentation. 


Towel Smoothing and Folding

We use the corner detection network to implement an algorithm that smooths and folds towels from a crumpled starting state. We present rollouts of the execution below.


IROS 2022 Video Submission

luv_vid_trimmed.mp4