# US 12,181,607 B2 · Systems and methods for occlusion detection > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,181,607 B2 - Document ID: US12181607B2 - Status: Granted - Kind: B2 - Application number: 17/134,283 - Filed: 2020-12-26 - Published: 2021-07-01 - Granted: 2024-12-31 - Earliest claimed: 2019-12-27 - Assignees: Waymo LLC - Applicants: Waymo LLC - Inventors: Jason Watson; Blaise Gassend - Web page: https://patentgrep.com/patent/US12181607B2 ## CPC - G01S 7/4817: {relating to scanning} - G01S 7/497: Means for monitoring or calibrating - G01S 17/86: Combinations of lidar systems with systems other than lidar, radar or sonar, e.g. with direction finders - G01S 17/89: for mapping or imaging - G01S 17/931: of land vehicles - G06T 7/246: using feature-based methods, e.g. the tracking of corners or segments - G06V 10/141: Control of illumination - G06V 20/56: exterior to a vehicle by using sensors mounted on the vehicle - G01S 2007/4975: {of sensor obstruction by, e.g. dirt- or ice-coating, e.g. by reflection measurement on front-screen} - G01S 2007/4977: {including means to prevent or remove the obstruction} - G06T 2207/10016: Video; Image sequence - G06T 2207/10048: Infrared image - G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES - G06T: IMAGE DATA PROCESSING OR GENERATION, IN GENERAL - G06V: IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING ## Abstract The present disclosure relates to systems and methods for occlusion detection. An example system includes a primary reflective surface and a rotatable mirror configured to rotate about a rotational axis. The rotatable mirror includes a plurality of secondary reflective surfaces. The system also includes an optical element and a camera that is configured to capture at least one image of the optical element by way of the primary reflective surface and at least one secondary reflective surface of the rotatable mirror. ## Claims ### Claim 1 A system comprising: a primary reflective surface; a rotatable mirror configured to rotate about a rotational axis, wherein the rotatable mirror comprises a plurality of secondary reflective surfaces; an optical element; and a camera, wherein the camera is configured to focus on the optical element to capture at least one image of the optical element by way of the primary reflective surface and at least one secondary reflective surface of the rotatable mirror. ### Claim 2 (depends on 1) The system of claim 1, further comprising a controller having at least one processor and a memory, wherein the at least one processor executes program instructions stored in the memory so as to carry out operations, the operations comprising: causing the rotatable mirror to rotate about the rotational axis; and causing the camera to capture a plurality of images of the optical element by way of the primary reflective surface and at least one secondary reflective surface of the rotatable mirror, wherein each image of the plurality of images is captured at a corresponding mirror angle of the at least one secondary reflective surface. ### Claim 3 (depends on 2) The system of claim 2, further comprising an illuminator, wherein the operations further comprise: while causing the camera to capture the plurality of images, causing the illuminator to emit light in a stroboscopic manner so as to illuminate the optical element by way of the primary reflective surface and the rotatable mirror. ### Claim 4 (depends on 3) The system of claim 3, determining an aggregate image of the optical element based on the plurality of images and the corresponding mirror angles of the at least one secondary reflective surface. ### Claim 5 (depends on 3) The system of claim 3, wherein the operations further comprise: determining, based on an aggregate image, that at least one occlusion object is present on the optical element. ### Claim 6 (depends on 1) The system of claim 1 further comprising an illuminator configured to emit light to illuminate the optical element by way of the primary reflective surface and the rotatable mirror. ### Claim 7 (depends on 6) The system of claim 6, wherein the illuminator comprises an infrared light-emitting diode (LED). ### Claim 8 (depends on 1) The system of claim 1, wherein the primary reflective surface comprises a rectangular mirror. ### Claim 9 (depends on 8) The system of claim 8, wherein the primary reflective surface comprises an aspect ratio of at least 8:1. ### Claim 10 (depends on 8) The system of claim 8, wherein a long axis of the primary reflective surface is disposed substantially parallel to the rotational axis. ### Claim 11 (depends on 1) The system of claim 1, wherein camera comprises a fixed focal length lens configured to focus on the optical element by way of the primary reflective surface and the at least one secondary reflective surface. ### Claim 12 (depends on 1) The system of claim 1, wherein the camera comprises a fixed focal length lens configured to focus the camera on the optical element. ### Claim 13 (depends on 1) The system of claim 1, wherein a shape of the rotatable mirror comprises at least one of: a rectangular prism or a triangular prism. ### Claim 14 A light detection and ranging (lidar) system comprising: a transmitter; a receiver; an optical element; a rotatable mirror configured to rotate about a rotational axis, wherein the rotatable mirror comprises a plurality of secondary reflective surfaces; a camera, wherein the camera is configured to focus on the optical element to capture at least one image of the optical element by way of at least one secondary reflective surface of the rotatable mirror; and a controller having at least one processor and a memory, wherein the at least one processor executes program instructions stored in the memory so as to carry out operations, the operations comprising: causing the rotatable mirror to rotate about the rotational axis; and causing the camera to capture a plurality of images of the optical element by way of at least one secondary reflective surface of the rotatable mirror, wherein each image of the plurality of images is captured at a corresponding mirror angle of the at least one secondary reflective surface. ### Claim 15 (depends on 14) The lidar system of claim 14, determining an aggregate image of the optical element based on the plurality of images and the corresponding mirror angles of the at least one secondary reflective surface. ### Claim 16 (depends on 14) The lidar system of claim 14, wherein the operations further comprise: determining, based on an aggregate image, that at least one occlusion object is present on the optical element. ### Claim 17 A method comprising: causing a rotatable mirror to rotate about a rotational axis, wherein the rotatable mirror comprises a plurality of secondary reflective surfaces; and causing a camera, which is focused on an optical element, to capture a plurality of images of the optical element by way of at least one secondary reflective surface of the rotatable mirror, wherein each image of the plurality of images is captured at a corresponding mirror angle of the at least one secondary reflective surface. ### Claim 18 (depends on 17) The method of claim 17 further comprising: determining an aggregate image of the optical element based on the plurality of images and the corresponding mirror angles of the at least one secondary reflective surface. ### Claim 19 (depends on 17) The method of claim 17, further comprising: determining, based on an aggregate image, that at least one occlusion object is present on the optical element. ### Claim 20 (depends on 17) The method of claim 17, further comprising: while causing the camera to capture the plurality of images, causing an illuminator to emit light in a stroboscopic manner so as to illuminate the optical element by way of a primary reflective surface and the rotatable mirror.