# How Self-Driving Cars Detect Dirty Lidar Sensors > Waymo's 2024 patent on a self-driving car system that uses two scans from a rotating Lidar sensor to spot dirt or obstructions on its lens. - **Patent:** US 12130389 - **Original title:** Methods and systems for detecting sensor occlusions - **Owner:** Waymo - **Granted:** 2024 - **Status:** Active - **Times cited:** 1 - **Field:** automotive, aerospace, consumer_electronics, robotics, ai_ml ## What it does This patent describes a method for a self-driving car's Lidar system to detect when its view is blocked. The Lidar sensor, which uses light to measure distances, has a housing that spins. As it spins, it sends out light pulses and measures how they bounce back, creating a 'scan' of its surroundings. This patent claims a system that takes two separate scans of the same area. By comparing these two scans, the system can identify if a part of the view is consistently missing or distorted, indicating something is blocking the Lidar's optical window, like dirt or a sticker. For example, if the first scan shows a clear road but the second scan shows a blurry patch in the same spot, the system knows something is obstructing the sensor. ## What it does NOT cover - Lidar systems that do not rotate their sensor housing. - Methods that only take a single scan of the environment. - Detecting occlusions using sensors other than Lidar. - Systems that do not compare multiple scans to identify blockages. - Identifying occlusions that are not on the optical window of the Lidar. ## The clever bit Instead of relying on external sensors to check for dirt, the system cleverly uses the Lidar's own scanning process. By comparing two scans taken from slightly different perspectives or at different times, it can infer an obstruction based on inconsistencies in the data itself. ## Real-world examples 1. Waymo self-driving vehicles 2. Lidar systems on autonomous vehicles ## Why it matters Lidar is crucial for self-driving cars to 'see' their environment. If the Lidar's sensors are dirty or blocked, the car's perception system can be severely impaired, leading to unsafe driving. This patent addresses a fundamental challenge in maintaining the reliability of these critical sensors in real-world conditions. ## Frequently asked questions ### What does How Self-Driving Cars Detect Dirty Lidar Sensors cover? Waymo's 2024 patent on a self-driving car system that uses two scans from a rotating Lidar sensor to spot dirt or obstructions on its lens. ### Who owns patent US 12130389? Waymo owns this patent, granted in 2024. ### When does this patent expire? This patent is expected to expire on March 10, 2041, when the invention enters the public domain. ### What is patent US 12130389 cited by? This patent has been cited by 1 later patents that build on its ideas. ### What problem does this patent solve? Lidar is crucial for self-driving cars to 'see' their environment. If the Lidar's sensors are dirty or blocked, the car's perception system can be severely impaired, leading to unsafe driving. This patent addresses a fundamental challenge in maintaining the reliability of these critical sensors in real-world conditions. ### What does this patent NOT cover? Lidar systems that do not rotate their sensor housing. **Full plain-English explainer:** https://patentbrief.org/patent/us/12130389/methods-and-systems-for-detecting-sensor-occlusions **Original patent:** https://patents.google.com/patent/US12130389 --- _Source: PatentBrief — https://patentbrief.org. Patent facts are from public records; the plain-English explanation is PatentBrief's._ ## Related patents Semantically similar inventions in the PatentBrief corpus: - [LiDAR System for Seeing Through Shiny Objects](https://patentbrief.org/patent/us/11041957/systems-and-methods-for-mitigating-effects-of-high-reflectivity-objects-in-lidar) — Toyota's patent on a LiDAR system that can ignore blinding reflections from shiny surfaces to better see what's around a vehicle. - [How Self-Driving Cars Find Clear Paths Between Objects](https://patentbrief.org/patent/us/10733420/systems-and-methods-for-free-space-inference-to-break-apart-clustered-objects-in) — This patent describes a method for vehicles, especially self-driving ones, to use lidar data and a 3D grid to precisely identify open spaces between obstacles, helping them navigate safely. - [Toyota's Patent on Detecting Road Hazards with LIDAR](https://patentbrief.org/patent/us/12292511/method-for-road-debris-detection-using-low-cost-lidar) — Toyota's 2025 patent describes a car system using LIDAR to spot road problems by comparing how light bounces off the road to a known 'good' road signal. - [How a Smart LIDAR System Adapts to Noise for Better Distance Sensing](https://patentbrief.org/patent/us/20240045038/noise-adaptive-solid-state-lidar-system) — This patent describes a LIDAR system that uses multiple lasers and detectors, and intelligently adjusts the electrical settings of specific detectors to reduce noise and improve distance measurements in different lighting conditions. - [How to Combine Wide-Angle LiDAR Depth with Standard Camera Images](https://patentbrief.org/patent/us/11543533/systems-and-methods-for-wide-angle-lidar-using-non-uniform-magnification-optics) — This patent describes a method for combining a wide-angle depth map from a LiDAR sensor, which has unevenly spaced pixels, with a standard camera image by first correcting the depth map's pixel distribution and then merging the two for a complete view.