▁that ▁uses ▁a ▁fr inge ▁pattern ▁project ed ▁from ▁a ▁high ▁definition ▁screen ▁to ▁capture ▁the ▁reflected ▁image ▁of ▁the ▁pattern ▁using ▁a ▁high ▁definition ▁camera . ▁ ▁The ▁sin us oid al ▁wave form ▁acts ▁like ▁a ▁r uler ▁over ▁the ▁surface ▁allowing ▁the ▁relative ▁ordin ates ▁of ▁the ▁light ▁source ▁points ▁to ▁be ▁quant ified ▁as ▁they ▁are ▁proportional ▁to ▁the ▁spatial ▁phase ▁of ▁the ▁sin us oid al ▁pattern ▁wave form . ▁By ▁using ▁a ▁standard ▁technique ▁known ▁as ▁“ phase ▁ste pping ” ▁ ▁accurate ▁measurement ▁of ▁each ▁point ▁across ▁the ▁surface ▁can ▁be ▁made ▁through ▁quant ifying ▁the ▁corresponding ▁point ▁per ▁pixel ▁on ▁the ▁camera . ▁▁ ▁Using ▁the ▁known ▁geometric ▁relationship ▁between ▁the ▁display , ▁the ▁object ▁surface ▁and ▁the ▁camera , ▁light ▁ray s ▁reflected ▁from ▁the ▁surface ▁can ▁be ▁spatial ly ▁model led ▁to ▁calculate ▁the ▁direction ▁of ▁the ▁normal ▁at ▁each ▁point ▁of ▁the ▁surface ▁thereby ▁allowing ▁the ▁profile ▁at ▁that ▁point ▁to ▁be ▁obtained . ▁By ▁displaying ▁the ▁sin us oid al ▁wave form ▁in ▁both ▁horizontal ▁and ▁vertical ▁directions ▁the ▁surface ▁s lop es ▁can ▁be ▁determined ▁in ▁both ▁orthogonal ▁directions . ▁▁ ▁By ▁differenti ating ▁the ▁measurement ▁data ▁the ▁curv ature ▁field ▁can ▁be ▁calculated ▁allowing ▁accurate ▁character isation ▁of ▁a ▁surface ▁profile . ▁To ▁simulate ▁the ▁human ▁eye ' s ▁resolution ▁at ▁various ▁distances ▁the ▁specific ▁band ▁pass ▁filtering ▁is ▁applied ▁to ▁the ▁curv ature ▁data ▁separ ating ▁the ▁structure ▁data ▁according ▁to ▁size : ▁ ▁Ka ▁ 0 .