Automatic tire identification and DOT code reading - Micro-Epsilon

A200_eProfile scannerscanCONTROLAutomatic tire identification and DOT code readingAs a car manufacturer for the North American market, itis a legal demand to save the production date of the tiresassembled to one car to a database.The information of the tire production date is written on thesidewall of the tire. Encoded in the DOT number (DOT -Department of Transportation). The DOT number includesthe production date and information on the tire and themanufacturer. Reading this number is a simple task for ahuman being.The automated way is a big challenge. Therefore Volvouse the scanCONTROL 2750-100 for this task.Black letters on black backgroundThe DOT number on a tire is embossed or raised in theblack rubber of the surface. The letters are therefore writtenblack on black and no standard vision camera can handlethis because of the low contrast. The scanCONTROL2750-100 is measuring the distance to the surface usingthe triangulation principle. The sensor delivers a heightimage of the tire directly into the application software. Ina height image dark is away from the sensor and brightis near to the sensor. The intensity values directly matchcalibrated measurement values. Therefore the applicationsoftware gets an image where the DOT number can befound due to local variation in the offset. Embossed lettersare brighter than the surrounding material and raisedare darker.3D view of a tire surfaceImage with scanCONTROL 2750-100Image with an usual high-end laser scanner360° scan of a complete tire – greyscale shows height information; red area is DOT number

applicationHigh speed & high accuracyThe tires have to be checked within maximum of4.5sec time to ensure that the complete process is notslowed down. So the scanCONTROL needs to workwith a very high speed on the low contrast surface. ThescanCONTROL 2750 is used with a profile frequency of2000 Hz and the sensor delivers over 1 Million calibratedmeasuring points per second. So one height image hasa resolution of up to 640 x 9,000 calibrated measuringpoints.The distance between each profile is 0.2mm as well asthe distance between two points within one profile in orderto create square pixels. Therefore a circle on the tyrelooks a circle in the image, not an ellipse.High data rateBecause the DOT number can be on different sides of thetire, the application uses two scanCONTROL 2750-100.One sensor for each side of the tire. The high data ratecan be achieved due to the high performance interfaceof the scanCONTROL sensors. Gigabit Ethernet orIEEE 1394 (Firewire) are available and capable to providethe bandwidth.Perfect synchronisationWhen the tire is turned 360 the movement is not continuous.The application requires defined distances betweeneach profile. So it is necessary to synchronize the tiremovement with the measurement. scanCONTROL 2750offers with its high performing trigger input an easy wayto solve this task.MICRO-EPSILONKönigbacherstr. 1594496 Ortenburg/GermanyTel. +49 (0) 85 42/1 68-0Fax +49(0) 85 42/1 69 90info@micro-epsilon.comwww.micro-epsilon.comA member of micro-epsilon groupCertified DIN EN ISO 9001 : 2000Modifications reserved / 9781200-A011090FHF