# US 12,111,424 B2 · Safety laser scanner and method for front screen monitoring > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,111,424 B2 - Document ID: US12111424B2 - Status: Granted - Kind: B2 - Application number: 17/169,019 - Filed: 2021-02-05 - Published: 2021-08-12 - Granted: 2024-10-08 - Earliest claimed: 2020-02-07 - Assignees: Sick AG - Applicants: Sick AG - Inventors: Joachim Krämer; Markus Hammes; Ino Geisemeyer - Web page: https://patentgrep.com/patent/US12111424B2 ## CPC - G01S 7/4868: {Controlling received signal intensity or exposure of sensor} - G01S 7/497: Means for monitoring or calibrating - G01S 7/4814: {of transmitters alone} - G01S 7/4817: {relating to scanning} - G01S 17/04: Systems determining the presence of a target - G01S 17/08: for measuring distance only (indirect measurement G01S17/46; active triangulation systems G01S17/48) - G01S 17/42: Simultaneous measurement of distance and other co-ordinates (indirect measurement G01S17/46) - G01S 2007/4975: {of sensor obstruction by, e.g. dirt- or ice-coating, e.g. by reflection measurement on front-screen} - 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 ## Abstract A safety laser scanner (10) for detecting objects in a monitored zone (20) is provided that has a light transmitter (12) for transmitting a scan beam (16), a movable deflection unit (18) for the periodic scanning of the monitored zone (20) by the scan beam (16), a light receiver (26) for generating a received signal from the scan beam (22) remitted by the objects, a front screen (38), and a control and evaluation unit (32) that is configured to acquire information on the objects in the monitored zone (20) from the received signal and to recognize an impaired light permeability of the front screen (38) in a front screen monitoring by evaluating a front screen reflection beam (54) that is generated from the scan beam (16) by reflection at the front screen (38), At least one light deflection unit (56, 58) is provided in the optical path of the front screen reflection beam (54) that guides the front screen reflection beam (54) to the front screen (38) again in a region (60) to be tested so that a twice-reflected front screen reflection beam (62) is produced by reflection at the region (60) to be tested. ## Claims ### Claim 1 A safety laser scanner (10) for detecting objects in a monitored zone (20) that has a light transmitter (12) for transmitting a scan beam (16), a movable deflection unit (18) for a periodic scanning of the monitored zone (20) by the scan beam (16), a light receiver (26) for generating a received signal from the scan beam (22) re-emitted by the objects, a front screen (38), and a control and evaluation unit (32) that is configured to acquire information on the objects in the monitored zone (20) from the received signal and to recognize an impaired light permeability of the front screen (38) in a front screen monitoring by evaluating a front screen reflection beam (54) that is generated from the scan beam (16) by reflection at the front screen (38), characterized by at least one light deflection element (56, 58) in the optical path of the front screen reflection beam (54) that guides the front screen reflection beam (54) to the front screen (38) again in a region (60) to be tested so that a twice-reflected front screen reflection beam (62) is produced by reflection at the region (60) to be tested. ### Claim 2 (depends on 1) The safety laser scanner (10) in accordance with claim 1, wherein the control and evaluation unit (32) is configured to evaluate the received signal generated by the twice-reflected front screen reflection beam (62) in the light receiver (26) for the front screen monitoring. ### Claim 3 (depends on 1) The safety laser scanner (10) in accordance with claim 1, that has at least one external additional light receiver (66) on which a portion (64) of the front screen reflection beam (54) transmitting the region (60) to be tested is incident and wherein the control and evaluation unit (32) is configured to evaluate the received signal of the additional light receiver (66) for the front screen monitoring. ### Claim 4 (depends on 1) The safety laser scanner (10) in accordance with claim 1, wherein the light transmitter (12) and the light receiver (26) are arranged next to one another with mutually parallel optical axes in a biaxial design. ### Claim 5 (depends on 1) The safety laser scanner (10) in accordance with claim 1, that has at least one pair of test light transmitters (44) and test light receivers (46) for the additional front screen monitoring that are arranged in the manner of a through beam light barrier or of a reflection light barrier to check a partial region of the front screen (38) for light permeability by a transmission measurement. ### Claim 6 (depends on 1) The safety laser scanner (10) in accordance with claim 1, wherein the at least one light deflection element (56, 58) is only provided in at least one partial region of a field of view of the safety laser scanner (10) so that the front screen monitoring based on the front screen reflection beam (54) only relates to the partial region. ### Claim 7 (depends on 6) The safety laser scanner (10) in accordance with claim 6, wherein the partial region is a marginal region between the field of view and a dead zone outside the field of view, with the at least one light deflection element (56, 58) in particular being provided in the dead zone. ### Claim 8 (depends on 7) The safety laser scanner (10) in accordance with claim 7, wherein the control and evaluation unit (32) is configured to adapt the sensitivity of the detection of the twice-reflected front screen reflection beam (62) in the light receiver (26) and/or the evaluation of the received signal thereby generated in the marginal region. ### Claim 9 (depends on 1) The safety laser scanner (10) in accordance with claim 1, wherein the front screen (38) has the shape of a rotational body and a curved contour in section, in particular a contour curved in cup shape. ### Claim 10 (depends on 1) The safety laser scanner (10) in accordance with claim 1, that has a first and a second light deflection element (56, 58) in the optical path of the front screen reflection beam (54), wherein the first light deflection element (56) is in particular arranged at a centrally arranged motor holder and the second light deflection unit (58) is arranged at a cover (42) of the safety laser scanner (10). ### Claim 11 (depends on 1) The safety laser scanner (10) in accordance with claim 1, wherein the at least one light deflection element (56, 58) is configured as beam attenuating; and/or wherein a reference light receiver is arranged in the optical path of the front screen reflection beam (54), in particular at the at least one light deflection element (56, 58). ### Claim 12 (depends on 1) The safety laser scanner (10) in accordance with claim 1, wherein the at least one light deflection element (56, 58) and a light trap are respectively partially arranged in the direction of revolution of the movement of the deflection unit (18) to enable a differential front screen monitoring by a comparison of the received signals. ### Claim 13 (depends on 1) The safety laser scanner (10) in accordance with claim 1, that is configured as a multilayer scanner having a plurality of scan beams separated in elevation, with at least one of the scan beams being used for the front screen monitoring. ### Claim 14 (depends on 1) The safety laser scanner (10) in accordance with claim 1, that has a safe output (34) and whose control and evaluation unit (32) is configured to compare the position of detected objects with protected fields and to control the safe output (34) by a safeguarding signal on recognition of an unauthorized protected field intrusion. ### Claim 15 A method of front screen monitoring of a front screen (38) of a safety laser scanner (10), in particular of a safety laser scanner (10) in accordance with any one of the preceding claims, wherein a scan beam (16) is transmitted, the monitored zone (20) is periodically scanned by the scan beam (16), a received signal is generated from the scan beam (22) re-emitted by objects in the monitored zone (20) and is evaluated to acquire information on the objects and to recognize an impaired light permeability of the front screen (38) by evaluating a front screen reflection beam for the front screen monitoring that is generated from the scan beam by reflection at the front screen (38), characterized in that the front screen reflection beam (54) is again guided by at least one light deflection element (56, 58) to the front screen (38) in its optical path in a region (60) to be tested so that a twice-reflected front screen reflection beam (62) is produced by reflection at the region (60) to be tested.