INVESTIGATIONS ON AMBIGUTY UNWRAPPING OF RANGE IMAGES

Transcription

1 In: Bretr F, Pierrot-Deseilligny M, Vosselmn G (Es) Lser snning 2009, IAPRS, Vol. XXXVIII, Prt 3/W8 Pris, Frne, Septemer 1-2, 2009 INVESTIGATIONS ON AMBIGUTY UNWRAPPING OF RANGE IMAGES B. Jutzi Institute of Photogrmmetry n Remote Sensing, Universität Krlsruhe Kiserstr. 12, Krlsruhe, Germny oris.jutzi@ipf.uni-krlsruhe.e KEY WORDS: Rnge imging, RIM, miguous, phse-unwrpping, moultion frequeny, lose rnge. ABSTRACT: For the first time the si priniple to unify vntges etween tive sensors n the simultneous pturing of n imge for n extene re of ynmil 3D pplitions in lose rnge is given y rnge imging (RIM) sensors. The rwk of t whih is pture with RIM sensors is the solute rnge ury n the limite non-miguity rnge. From other sensor systems ifferent tehniques re known to solve this prolem in orer to otin non-miguity rnge, e.g. y utilizing ifferent moultion frequenies s most ontinuous-wve (CW) moulte lser snner n rr systems o or y (pseuo) rnom moultion. In this pper post-proessing tsk is presente. The Golstein 2D unwrpping proeure for unwrpping the rnge miguities of rnging sensors (e.g. RIM sensors or CW-moulte lser snners) is propose onsiering resiues, rnh uts n tree estimtion strtegies n itionlly onfiene riteri. It oul e shown tht rnge restortion for numerous perios of the miguity rnge is in priniple possile with the presente 2D unwrpping proeure. 1. INTRODUCTION Currently the geometril 3D pturing n esription of the environment re se on imge or rnge t. By utilizing pssive imging sensors the 3D informtion is gine y texture imge t iniretly from severl imges with ostly stereo- or multiple imge nlysis. These proeures re wiely use, ut hve inispensle lims ue to pturing isposition n sene ontents. For instne the illumintion onitions shoul e equte, the oserve mterils shoul e texture n opque, n the istne etween ojet n mer s well s etween the mer viewpoints of stereo imges shoul e suffiient lrge enough for gining relile 3D reonstrution. Besie this the photogrmmetri methos re omplemente y lser snner proeures. These tive sensors pture sequene of singulr rnge vlues while omplishing time epenent sptil snning of the environment. Besie these si rnge mesurements the urrent ommeril irorne lser snner (ALS) evelopments llow to reor the mplitue or the wveform of the ksttere lser pulse (Jutzi & Still, 2006). Therefore, lser snner systems like OPTECH ALTM 3100, TOPEYE MK II, n TOPOSYS HARRIER 56 n e use. The ltter system is se on the RIEGL LMS-Q560. More n more wveform pturing snners re ville t the moment, e.g. RIEGL - one of the leing ompnies for lser snners - lrey offers severl snners (LMS-Q560, LMS-Q680, n VQ-480). In generl speorne, irorne s well s terrestril lser snner sensors llow iret n illumintion-inepenent mesurement of 3 ojets (Shn & Toth, 2008). For n urte t quisition neessrily the sene ontents s well s the sensor pltform shoul e stti, otherwise eformtion of the environment n pper. In generl with n inresing ynmi of the sene ontents respetively sensor pltform the omplexity of the nlysis inreses n the exploittion of 3D informtion is more n more hllenging. To gin three-imensionl informtion from rpi ynmil proesses the pturing of the environment t the sme time is essentil. Very reently enhne types of tive imging sensors hve strte to meet these requirements, nmely the Swiss Rnger ( the PMD Vision ( n the O3D series ( These lose rnge sensors (Tle 1) llow to pture n rnge imge n o-registere intensity imge simultneously with high repetition rte (up to 100 releses per seon). The nonmiguity rnge is urrently elow 7.5m n epens on the moultion frequeny. The mesure intensity strongly epens on the use wvelength (usully lose infrre) of the lser soure n the surfe hrteristi. For the first time the si priniple to unify vntges of tive sensors n the simultneous pturing of n imge for n extene re of ynmil 3D pplitions is given. Espeilly the 3D monitoring in lose rnge with irorne n terrestril pltforms in prolemti wether n illumintion onitions or t night is promising with this novel tehnology. Therefore ifferent pplitions re uiling surveillne, trffi monitoring, n river ssistne. Besie this, the 3D motion or eformtion nlysis, like utonomous nvigtion of roots, trjetory trking of peestrins for surveying, or mker free 3D mesurements of rsh tests, re of interest. Another tehnil vntge is the monostti sensor onfigurtion, whih llows to oserve the re of interest from single point of view, in ontrst to the lssil stereo oservtion tehniques with pssive sensors, whih nee t lest two ifferent viewpoints. The myor rwks re the limite non-miguity rnge n the solute rnge ury of few entimeters. Espeilly the reltively lrge noise influene on the mesurement, ue to the lrge mount of mient rition in omprison to the emitte rition, results in rnge mesurement whih is less relile ompre to the performne of irorne or terrestril lser snner (TLS). However onerning the tehnil progress, most limittions will e overome soon n in lose future systems with expne operting rnge n improve imge size will e ville. The terminology for snnerless rnge imging systems is multifrious, the terms Time-of-Flight (TOF) epth mer, 3D rnge imger, Time-of-Flight Sensors, photoni mixer evies (PMD; Shwrte, 1997), or often omintion of the mentione terms re use. Unfortuntely, most of the terms re muh more relte to the rnge mesurement thn on the s well ville gry vlue mesurement of the oserve re. For the proeure the term rnge imging with the revition RIM is more n more estlishe, espeilly in Europe. Vrious stuies out rnge imging hve een pulishe in the literture eling with ifferent interests. Besie the hrwre n sensor evelopments (Lnge, 2000), nowys most works fous on geometri n riometri lirtion: 265

2 In: Bretr F, Pierrot-Deseilligny M, Vosselmn G (Es) Lser snning 2009, IAPRS, Vol. XXXVIII, Prt 3/W8 Pris, Frne, Septemer 1-2, 2009 Reulke (2006) introue geometril lirtion n fuse the intensity imge erive y the rnge imging sensor with high resolution RGB t to improve the texturing of surfes. Khlmnn et l. (2007) fouse on the geometri lirtion of rnge imging sensors n evelope trking of moving ojets (people) pproh se on reursive Byesin filter. Lihti (2008) propose metho for the self-lirtion y unle justment of rnge imging sensors whih llows simultneous lirtion onerning the sptil istortions n the rnging system. Other works fouse on trking of ojets n utomti extrtion of ojet fetures: For the trking of humn motion n intertion within rnge imge sequene, Westfel & Hempel (2008) suggeste the omintion of omplementry riometri n geometri informtion to inrese ury n reliility. For moving rnge imging Krel et l. (2007) speifie n utomti ojet segmenttion sensor se on fst minimum ovrine eterminnt pproh n evlute sttistilly the qulity of the t. Kim et l. (2008) propose to utilize more thn one synhronize rnge imging system to gin multi views for the reonstrution of ynmi senes. As riefly mentione ove one rwk of the RIM sensors is the limite non-miguity rnge. From other sensor systems ifferent tehniques re known to solve this prolem in orer to otin non-miguity rnge, e.g. y utilizing ifferent moultion frequenies s most ontinuous-wve (CW) moulte lser snner n rr systems o or y (pseuo) rnom moultion. In this pper post-proessing tsk is investigte in ontrst to the ove mentione n not yet for RIM sensors ville tehnil improvements. It hs to e mentione tht the miguous rnge sujet is lose relte to the well known phse unwrpping prolem whih is extensively isusse in the rr interferometry ommunity. This inverse prolem nnot e solve in generl n intensive reserh is going on this issue until toy. For instne one lrge rwk is the sensitivity of the phse reonstrution to minor mesurement errors. Aitionlly, the reonstrution suffers from multiple integer solutions use y the unwrpping proeure. Usully the mesure environment is unknown n, therefore, multiple integer solutions re possile, if the topogrphy ontins lrge geometril isontinuities. In this pper metho for unwrpping the rnge miguities of rnge imging sensors is propose. In Setion 2 the mesurement priniple of rnge imging sensors, 1D stright forwr n the Golstein 2D unwrpping proeure re introue. In Setion 3 the sensor n sene onfigurtion is presente n in Setion 4 the t re exmine. The nlysis y the mentione unwrpping proeures is esrie in Setion 5 onsiering resiues, rnh uts n tree estimtion strtegies, n the onfiene riteri. Finlly, the erive results re evlute n isusse, the ontent of the entire pper is onlue, n n outlook is given. 2.1 Mesurement priniple 2. METHODOLOGY The rnge mesurement n e riefly esrie s follows: First sinusoil CW moulte signl is trnsmitte y LED rry in form of monohromti light. The emitte light trvels to the ojet, is ksttere y the illuminte surfe, n pture y reeiver rry (usully CCD or CMOS rrys). Conerning emoultion of the sinusoil reeive signl the prmeters mplitue A n phse φ n e etermine. For eh mesurement four neighorhoo pixels re utilize to mesure the four reeive intensities with reltive phse shift of 90, or with other wors n solute phse shift of 0, 90, 180, n 270. Then the phse shift φ etween the trnsmitte n reeive signl n e etermine y the intensity vlues A 0, A 90, A 180, n A 270, with ϕ rtn A A. (1) = A0 A180 Bse on the phse shift φ the rnge R to the ojet is given with respet to the two-wy time of flight y ϕ R = 2 f 2π, (2) where f m is the moultion frequeny n the spee of light. 2.2 Dt hrteristi & feture onvention The rnge miguity R n e enote y MESA Swiss Rnger PMD [Vision] Type SR-3000 SR-4000 O3 S3 CmCue 2.0 URL Imge size 176x x144 64x48 64x48 204x204 Fol length [mm] 8 10 TBD Fiel of View (FoV) [ ] 47.5x x x30 40x30 40x40 Pixel size [µm] 40x40 40x40 100x x100 TBD Wvelength [nm] Power (optil) [W] TBD Frme rte [1/s] mx mx. 54 mx. 25 mx. 20 mx. 25 Moultion frequeny [MHz] 20 29, 30, vrile Non-miguity rnge [m] Size [mm] 60x50x65 65x65x68 60x42x54 120x75x95 60x187x60 Outoor fesiility no yes yes yes yes Tle 1. Speifition overview of selete rnge imging sensors: MESA Swiss Rnger series ( n PMD Vision series ( URLs esse on June PMD [Vision] O3/S3 re equivlent to IFM ( O3D100/ O3D200, Suppression of kgroun illumintion. m 266

3 In: Bretr F, Pierrot-Deseilligny M, Vosselmn G (Es) Lser snning 2009, IAPRS, Vol. XXXVIII, Prt 3/W8 Pris, Frne, Septemer 1-2, 2009 R = 2 f m. (3) To estimte the solute rnge R for the miguity n integer k is multiplie with the rnge miguity R R = Rk. (4) To resolve the rnge miguity vrious methos re known in literture. A generl overview of the existing methos is given in Ghigli & Pritt (1998). Most of these pprohes el with 2D t sets. In ontrst to this, the pturing of sene with RIM system elivers 3D t set ompose out of voxels with two sptil oorintes x,y n one time oorinte t Q( x, y, t ), (5) where for eh voxel ifferent fetures re mesure, e.g. rnge R, intensity I, n onfiene-of-the-mesurement C. Then for eh feture single t ue is given y Q R, Q I, n Q C. In the following, sttionry sensor setup is ssume for oserving high ynmil temporl n sptil sene. Two methos were exmine n rief overview is given in the following Setions D stright forwr unwrpping With this stright forwr pproh seprility of the t set is ssume se on sequentil omplishe 1D unwrpping. Aitionlly, msk, whih is ville from the t ue Q C with the feture onfiene-of-the-mesurement, n e use to msk out unrelile voxels. The rwk of this pproh is tht only single voxel in the neighorhoo of the six onnete voxels (joint fes onnetion) is onsiere n the result epens on the proessing iretion n orer. Therefore the topology is priniplly ignore n ue to this, the 1D proessing uses n erroneous unwrpping whih results in stripe pttern. This inequte pproh ws implemente minly for omprison purposes n to visulize the prolemti of miguity rnge unwrpping. 2.4 Golstein 2D unwrpping The Golstein pproh is esrie in etil in vrious pulitions, e.g. Golstein et l Originlly it ws evelope for phse unwrpping in rr interferometry. The suggeste solutions to reonstrut the unknown phse n e nlogue trnsferre to the miguous rnge prolemti. A rief esription of unwrpping the miguous rnge will e given in this setion. The gol of unwrpping is to fin integers k whih n e e to the mesure vlues to gin ontinuous representtion. The mesure vlues re within yle of zero n the nonmiguity vlue. In generl phse unwrpping pprohes re se on proessing the hnges etween the pixels or respetive voxels in the iret neighorhoo y grient lultion. Then the vlues re integrte y preefine rules n finlly, if isontinuity is etete, the most likelihoo integer solution for unwrpping is e. To get resonle solution it is essentil to fin n optiml integrtion pth for the grient. The unwrpping proeure is highly over etermine. Therefore, ifferent onstrints hve to e ssume. The key ssumption is moerte hnges within the neighorhoo with reltive hnges elow the miguity vlue. Vlues ove re lle isontinuities n hve to e ypsse y the restortion proeure. The isontinuities n e reue to inonsistenies within the rnge vlues, so-lle resiues. Resiues re given if the sum of four neighorhoo pixels lulte in irulr iretion is unequl to zero. This proeure is pth epenent n further it is very sensitive to noise. The ientifie resiues re onnete to generte so-lle rnh uts. Usully the length of the rnh uts (istne etween the resiues) shoul e s short s possile. The ie ehin the rnh ut is to fin lose y negtive n positive resiues (sometimes lle ipoles) whih n e ompenste y eh other if the totl hrge long the rnh ut is zero. If the totl hrge is nonzero, the serh ontinues for itionl lose y resiues. Eh ssoite resiue is onnete to the tree y mens of rnh ut n the totl hrge is lulte. If the totl hrge is zero the tree is onsiere. The isvntge of this proeure is tht oorintes (position) of the rnh uts re ritrrily hosen leving out importnt ontext informtion. A etter solution might e to utilize more expensive pproh, like for instne the Msk-ut-lgorithm, whih tke into ount the qulity onerning the position of the selete uts. For the ontinutive serh of ssoite resiues, regrless if the resiues hve een previously ssigne, they re e to new tree. This results in enriti form of the rnh uts. Finlly, the erive tree hs to e ypsse for the integrtion lultion to utilize the unwrpping proeure. This proeure n e itionlly supporte y the onfieneof-the-mesurement to msk out unrelile rnge vlues. 3.1 Sensor 3. CONFIGURATION For the investigtions Swiss Rnger SR-4000 sensor ws use with the speifitions liste in Tle 1. The sensor hs 176 x 144 pixel rry with pixel size n pith (sping) of out 40 µm. The user n preselet the moultion frequeny with 29, 30, n 31 MHz, whih results in mximum nonmiguity rnge of 5.17, 5.00, n 4.84 m. The mximum frme rte is out 50 frmes per seon. Therefore, the numer of 3D points mesure y rnge imging system is ove one million points per seon whih is equivlent to the urrent point pturing rte of the fstest lose rnge lser snners. 3.2 Sene A rnge imge sequene of n inoor sene ws reore y sttionry ple sensor. 100 frmes were pture with frme rte of 12 frmes per seon while the person ws moving in iretion to the sensor within furnishe room. A single RGB imge of the oserve sene is epite in Figure 1. For the environment no referene t onerning the riometry or geometry were ville. Figure 1. RGB imge of the oserve inoor sene. 267

4 In: Bretr F, Pierrot-Deseilligny M, Vosselmn G (Es) Lser snning 2009, IAPRS, Vol. XXXVIII, Prt 3/W8 Pris, Frne, Septemer 1-2, DATA EXAMINATION To epit the neighorhoo reltions of the feture rnge, the t ue ws slie in ifferent iretions: equivlent to the pture frmes in y-x slies, vertilly in t-y slies, n horizontlly in x-t slies. The sme proeure ws one for the feture intensity. Figure 2 shows set of imges for the ifferent slies in the spe-spe n spe-time omin with the orresponing rnge n intensity imges. The imges hve een normlize for visuliztion purposes n rnge n intensity vlues re epite s gry vlues. Besie the feture rnge n intensity the onfiene-of-themesurement is ville. In Figure 3 the qulity of the mesurement is oe y gry vlues, rk vlues for low onfiene () n right vlues for high onfiene (goo). Oviously the mesurements lose to the miguity rnge pper with signl-to-noise rtio n, therefore, the onfiene is low. Furthermore, the qulity of the mesurement is rnge epenent, mesurements in fr rnge re less relile thn in lose rnge. This n e oserve for instne t the wll on the left sie of the room. Further if the mesure intensity is ove the ynmi rnge, the reeiver sturtes n the mesurement is unusle. The sttisti of the qulity for the investigte slie is epite in Figure 3. It n e seen tht most of the mesurements re relile, ut out 11% of the mesurements re unrelile, where the onfiene-of-themesurement C is equivlent to Numer of elements Confiene ( < goo) Figure 3. Confiene-of-the-mesurement imge () n orresponing histogrm () for x-y slie. 5. ANALYSIS RESULTS 5.1 1D stright forwr unwrpping e Figure 2. Corresponing rnge n intensity imges ifferently orientte: &) x-y, &) t-y, n e&f) x-t slie. For the mesurements moultion frequeny of 29 MHz ws selete whih results in rnge miguity of R=5.17 m. The rnge miguity is elow the extension of the room. Figure 2 oviously shows severl rnge miguity rossings. The isontinuities of the gry vlues n e seen y ompring them with the ontinuous pperne of the gry vlues of the intensity in Figure 2, e.g. on the pln wll on left sie. Further the rnge n slope epenent mesure intensity vlues, whih erese with inresing rnge, re notiele on the wll n on the eiling. The intensity I n e normlize y the orresponing rnge r with 1 I. (6) 2 r Due to the sttionry sensor setup the t-y n x-t slies ontin minly stripy pttern, whih is typil for stti sene. This pttern is interrupte y speifi representtion of the ynmi proeures within the sene, whih n e reognize s motion re. In Figure 2-f the moving person is visile, ut the representtion is oviously eforme. In Figure 2&e within the motion re the lk to white rossover of the regions shows n ojet (person) rossing the miguity rnge uring the mesurements. f Rnge [m] The 1D stright forwr unwrpping oes not tke into ount ll neighorhoo reltions. An exmple for the unwrpping proeure is epite, where in Figure 4 the originl miguous rnge (she re line), the miguity rnge (otte green line), n the 1D unwrppe rnge (soli lue line) re shown. Furthermore, the orresponing intensity vlues re presente in Figure 4. Compring the hrteristi of the miguous rnge with the intensity vlues, the unreliility of the mesure vlues is ovious (e.g. t pixel oorinte 25). At this rnge the intensity vlues re noisy ompre to the nery vlues. After unwrpping the ynmi rnge intervl implies out four perios of the rnge miguity R in the epite exmple Pixel oorinte Intensity Pixel oorinte Figure 4. 1D exmples for the hrteristi of orresponing rnge n intensity vlues of single row: ) Originl miguous rnge (she re line), miguity rnge (otte green line), n 1D unwrppe rnge (soli lue line), ) intensity (soli green line). Utilizing this pproh on the x-y slies it n e shown tht the erive results epen on the unwrpping iretion ue to the isontinuities of the rnge vlues. In Figure 5 the results for ifferent proessing iretions re presente. Most of the 268

5 In: Bretr F, Pierrot-Deseilligny M, Vosselmn G (Es) Lser snning 2009, IAPRS, Vol. XXXVIII, Prt 3/W8 Pris, Frne, Septemer 1-2, 2009 filures re inue y unrelile mesurements, whih will e emonstrte in the following Setion. rnge res it is interite to ross the rnh uts. The numer of gine rnge offsets R oe y integer vlues re epite in Figure 6. For the lk res the numer is zero, this enotes the originl rnge is lrey non-miguous. The gry res show tht miguous rnge res hve een etete n solutions up to rnge miguity of four perios (right gry res) oul e etermine. Conerning the resiues on the fore mentione 1D stright forwr unwrpping pproh in Setion 5.1 it n e esily shown with Figure 7 tht the remining isontinuities erive y the erroneous rnge unwrpping hve their origin t the oorintes of the resiues (lk pixel). Figure 5. 1D stright forwr unwrpping results for ifferent proessing iretions: ) Right to left, ) ottom to top, ) left to right, ) top to ottom. 5.2 Resiues, rnh uts n tree estimtion First, ll resiues re lulte for ll x-y slies of the t ue Q R. In Figure 6 the negtive n positive resiues (lk n white olore pixels) for the x-y slie in Figure 2 re epite. All in ll 64 resiues were etermine. To proof the reliility of the resiues for eh resiue the orresponing onfiene-of-the-mesurement voxel is extrte. A histogrm with the sttisti for the reliility of ll resiues is epite in Figure 6. It lerly shows tht most of the etermine resiues se on n unrelile mesurement, s 26 resiues hve the onfiene-of-the-mesurement 0 n, therefore, they re unrelile. This oinies with the lrey mentione sttement tht the proeure to lulte resiues is very sensitive to noise. Numer of elements Confiene ( < goo) Figure 7. Visuliztion of resiues (lk pixel) n 1D stright forwr unwrpping results of Figure 5&. 5.3 Golmn 2D unwrpping onerning the onfiene riteri The given t ue Q C (onfiene-of-the-mesurement) provies informtion out the qulity of the mesurement, where the rnking of the qulity is within the intervl 0-7 n the vlues strt from unrelile (vlue 0) up to exellent (vlue 7). A histogrm for single x-y slie is shown in Figure 3. In the following the qulity of the mesurement on the reonstrution of the solute rnge is investigte. Therefore, ifferent tests were rrie out to verify the influene of the qulity of the mesurement on the reonstrution of the solute rnge. Overll seven tests were rrie out y utilizing the onfiene msks to verify the influene of the qulity of the mesurement on the reonstrution for the solute rnge y the 2D unwrpping proess. Only the relile miguity rnge vlues ove given threshol re onsiere for proessing. Aoring to this the low qulity mesurements hve een rejete. Selete results re epite in Figure 8. In lose rnge, elow two perios of the miguity rnge n with moest isontinuities the rnge unwrpping is relile (e.g. the wll on the left sie). Erroneous rnge unwrpping n e oserve in ll four results, where most of the wrong unwrpping rnge vlues pper t fr rnge, ove two perios of the miguity rnge. At this rnge the t qulity is poor n the rnge vlues might e noisy. In ition to this, numerous isontinuities re t this rnge. Furthermore, it hs to e mention tht the results minly epen on the see point initiliztion n on the onnetivity of the segments. Figure 6. Intermeite results: ) Extrte resiues, ) reliility of the resiues, ) rnh uts n trees, ) numer of gine rnge offsets R. In Figure 6 ll onnete resiues in form of rnh uts re shown, where ll rnh uts re linke together to the finl trees. For the following integrtion proeure to unwrp the 269

6 In: Bretr F, Pierrot-Deseilligny M, Vosselmn G (Es) Lser snning 2009, IAPRS, Vol. XXXVIII, Prt 3/W8 Pris, Frne, Septemer 1-2, CONCLUSION AND OUTLOOK Figure 8. Unwrpping results onsiering onfiene msks: ) Intervl 0-7 (equivlent to ll t proessing), ) intervl 2-7, ) intervl 4-7, n ) intervl Rnge epenent intensity normliztion Finlly, the rnge epenent orretion of the mesure intensity is lulte y utilizing Formul 4. The mesure intensity (Figure 2) n e ompre with the rnge orrete intensity (Figure 9). The erive intensity for the sme mteril (e.g. wll on the left) is equlize over the omplete rnge re. Of selete 1D exmple (otte white line in Figure 9) the orresponing intensity vlues (soli lue line) re epite in Figure 9. For omprison purposes the mesure intensity (soli green line) n the unwrppe rnge orrete intensity (she re line) is shown. Still some rtifts re remining from unrelile pixels t the 1D exmple n within the intensity imge (e.g. t the person). Intensity Pixel oorinte Figure 9. Rnge orrete intensity. ) Imge, ) 1D exmple. 6. EVALUATION AND DISCUSSION The evlution of the results is iffiult euse geometri n riometri referene t re not ville. Therefore, the evlution ws performe y visul riteri. It oul e oserve tht the rnge unwrpping sometimes fils, where most of the wrong rnge vlues pper t fr rnge, ove two perios of the miguity rnge, euse t this rnge the t qulity is poor n the rnge vlues might e noisy. However, in generl n improvement oul e gine. Oviously the min isvntge of the Golmn 2D unwrpping pproh is the wy the rnh uts re etermine euse they were selete y the riteri to e s short s possile (Figure 6) n they o not rely on topogrphil spets. This shoul e improve y more expensive pprohes, like e.g. the Msk-ut-lgorithm, whih tke into ount the qulity onerning the position of the selete uts. In generl the reonstrution suffers from multiple integer solutions if the topogrphy ontins lrge geometril isontinuities. By onsiering the onfiene-of-the-mesurement the result oul e further improve, ut in this se it is lwys tre of etween inomplete n erroneous results. It oul e shown tht rnge restortion for numerous perios of the miguity rnge is in priniple possile with the presente 2D unwrpping proeures. For future work the onfiene-of-the-mesurement might e relile sis for qulity guie unwrpping pproh. Furthermore, ue to the vilility of 3D t set, 3D unwrpping proeure might e promising. Besie these pprohes whih minly se on single sensor system, the utiliztion of more thn one synhronize rnge imging system to gin multi views might e of interest to solve the rnge unwrpping prolem. ACKNOWLEDGEMENT The uthor woul like to thnk the memers of MESA Imging for ssistne uring the mesurements. REFERENCES Ghigli, D. C., Pritt, M. D., Two-Dimensionl Phse Unwrpping: Theory, Algorithms, n Softwre. John Wiley & Sons: New York. Golstein, R. M., Zeker, H. A. Werner, C. L., Stellite rr interferometry: two-imensionl phse unwrpping. Rio Siene, 23, pp Jutzi, B., Still, U., Rnge etermintion with wveform reoring lser systems using Wiener Filter. ISPRS Journl of Photogrmmetry & Remote Sensing 61 (2): pp [oi: /j.isprsjprs ] Khlmnn, T., Remonino, F., Guillume, S., Rnge imging tehnology: new evelopments n pplitions for people ientifition n trking. In: Berlin, J.-A., Remonino, F., Shortis, M. R. (Es.) Vieometris IX, SPIE Proeeings Vol. 6491, 64910C. Krel, W., Dorninger, P., Pfeifer, N., In Situ Determintion Of Rnge Cmer Qulity Prmeters By Segmenttion. In: Gruen A, Khmen H (Es.) Optil 3-D Mesurement Tehniques VIII, pp Kim, Y. M., Chn, D., Theolt, C., Thrun, S., Design n lirtion of multi-view TOF sensor fusion system. In Proeeings of IEEE CVPR Workshop on Time-of-flight Computer Vision June 2008, pp Lnge, R., D time-of-flight istne mesurement with ustom soli-stte imge sensors in CMOS/CCD-tehnology. PhD thesis, University of Siegen. Lihti, D. D., Self-Clirtion of 3D Rnge Cmer. Interntionl Arhives of Photogrmmetry, Remote Sensing n Sptil Geoinformtion Sienes 37 (Prt B5), pp Reulke, R., Comintion of istne t with high resolution imges. In: Ms, H.-G., Shneier, D. (Es.) ISPRS Commission V Symposium: Imge Engineering n Vision Metrology, Interntionl Arhives of Photogrmmetry, Remote Sensing n Sptil Geoinformtion Sienes 36 (Prt B). Shwrte, R., Xu, Z., Heinol, H.-G., Olk, J., Klein, R., Buxum, B., Fisher, H., Shulte, J., New eletro-optil mixing n orrelting sensor: filities n pplitions of the photoni mixer evie (PMD). In: Loffel, O. (E.) 3D Sensors n 3D Imging, SPIE Proeeings Vol. 3100, pp Shn, J., Toth, C.K., (Es.) Topogrphi Lser Rnging n Snning: Priniples n Proessing. Bo Rton, FL: Tylor & Frnis. Westfel, P., Hempel, R., Rnge Imge Sequene Anlysis y 2.5-D Lest Squres Trking with Vrine Component Estimtion n Roust Vrine Covrine Mtrix Estimtion. Interntionl Arhives of Photogrmmetry, Remote Sensing n Sptil Geoinformtion Sienes 37 (Prt B5), pp