METRIC ALIGNMENT OF LASER RANGE SCANS AND CALIBRATED IMAGES USING LINEAR STRUCTURES Lorenzo Sorg CIRA the Italan Aerospace Research Centre Computer Vson and Vrtual Realty Lab.
Outlne Work goal Work motvaton State of the art Calbraton model Implementaton detals Results
Work Objectve The goal s the estmaton of rgd moton transformaton between a Laser Range Scanner and an Imagng System (External Calbraton), whch s needed to acheve the accurate algnment of the 3D range profles on a matched vdeo. ( R, t) : R SO(3), t 3
Work Motvaton The accurate co-regstraton of heterogeneous data s a fundamental requrement for a robotc systems, performng autonomous operatons: Object pose estmaton, dockng, trackng, graspng, etc.; Rover Autonomous Navgaton, Laser aded vsual SLAM; Geometrc documentaton and object nspecton; Sensor aded exposure of magng systems; anytme range profles and mage raster maps need to be jontly processed to gather knowledge about the surroundng envronment.
State of the art!! No extensve lterature s avalable on ths topc. I. P. Núñez and al. - Data Fuson Calbraton for a 3D Laser Range Fnder and a Camera usng Inertal Data. (ECMR 2009). II. R. Unnkrshnan and al. - Fast extrnsc calbraton of a laser rangefnder to a camera. Techncal Report CMU-RI-TR-05-09. III. L. Huang and al. - A Novel Mult-Planar LIDAR and Computer Vson Calbraton Procedure Usng 2D Patterns for Automated Navgaton. IEEE Intellgent Vehcle Symposum 2009. IV. S. Kumar and al. - Sensor Fuson of Laser & Stereo Vson Camera for Depth Estmaton and Obstacle Avodance. Int. Journal of Computer Applcatons. Num. 26:3. Need of a mddle-man sensor (AHRS); Algorthm do not cope wth 1D lasers scanners; Geometrc entty used for calbraton may not be easly and accurately extracted from raw data (planes); Not real calbraton (generaton of rough navgaton maps);
Calbraton Model SE(3) H C S L Geometrc Entty Camera Laser Scanner Back-projected plane l Image lne 0 1 1 l P H P C S C S C P
Calbraton Model L 1,..., N C l C 1,..., N 1,..., N S P 1,..., N H SC mn HSE(3) 1.. N d C SC S C T S, H P l R P t 1.. N
Calbraton Tool Implementaton Detals
Implementaton Detals Lne extracton from mages Lne Detecton by Hough Transform (RED) Lne Refnement Based on GL 10 Flterng (GREEN) Bsector Segment Extracton (YELLOW) C l 1,..., N L.Sorg - Edgelet Trackng usng Gauss-Laguerre Crcular Harmonc Flters. Paper submtted to IEEE ICIP 2011.
Implementaton Detals Lne extracton from range profles Spot Detecton by maxmum curvature k r 2 2r' 2 rr'' 3 2 2 r r' 2 Spot Refnement by Local Parabolc Fttng S P 1,..., N
Implementaton Detals External Calbraton estmaton External calbraton ntalzaton by vsual nspecton ( easy! ) 1 0 0 0 R z H dp J d d t P R dr l P H d d S T C S C S C 0, Implct enforcement of SO(3) constrant n LM scheme; Analytcal computaton of error terms Jacoban. T T T S T C d S T C d d dp I t P R l J t P R l d 3 0
Results on synthetc data Synthetcally generated scene gven by 20 lnes n 3D space; Image ponts corrupted by addtve whte Gaussan nose; Nose std.dev. rangng n the nterval [0-10] px; 100 test for each nose level. e rot R T Rˆ 180 [deg] e tr t tˆ 100 t [%] N N
Results on synthetc data Synthetcally generated scene gven by N lnes n 3D space; Image ponts corrupted by addtve whte Gaussan nose wth fxed ntensty ( 3 px std.dev.) ; Numer of lnes rangng n the nterval [5-200]; 100 test for each scene complexty level. e rot R T Rˆ 180 [deg] e tr t tˆ 100 t [%] Nlnes Nlnes
Laser Camera system Results on real system Pont Grey Chameleon 1296(H) x 964(V) 6 mm lens (43 H Fov) Hokuyo Scannng Range Fnder UTM-30LX 30m x 270 scannng range 0.25 angular resoluton Accuracy ±30mm [ 0.1m : 10 m ]
Results on real system Optmzaton Process dp dp 0 Err Err 0 t
Results on real system Optmzaton Process
Results
Results
Results
Conclusons A technque to estmate the External Calbraton of a Laser-Camera system has been proposed; The technque uses 3D straght lnes as calbraton geometrcal entty; Support algorthms have been defned to accuratly collect the calbraton dataset from laser profles and mages; The algorthm provdes a core utlty for any multsensor platform performng some robotc operaton (object trackng, pose estmaton, scene exploraton, geometry retrval, etc. ); The algorthm s sutable for offlne calbraton and onlne calbraton recovery; Straghforward extenson to the case of stereocamera or multcamera.
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