▁definition ▁of ▁is chem ia , ▁spe ck le ▁tracking ▁seems ▁a ▁valuable ▁ende avor . ▁This ▁spe ck le ▁pattern ▁is ▁a ▁mixture ▁of ▁inter ference ▁patterns ▁and ▁natural ▁ac oust ic ▁ref lections . ▁These ▁ref lections ▁are ▁also ▁described ▁as ▁spe ck les ▁or ▁markers . ▁The ▁pattern ▁being ▁random , ▁each ▁region ▁of ▁the ▁my oc ard ium ▁has ▁a ▁unique ▁spe ck le ▁pattern ▁( also ▁called ▁patterns , ▁features , ▁or ▁finger print s ) ▁that ▁allows ▁the ▁region ▁to ▁be ▁trac ed ▁from ▁one ▁frame ▁to ▁the ▁next , ▁and ▁this ▁spe ck le ▁pattern ▁is ▁relatively ▁stable , ▁at ▁least ▁from ▁one ▁frame ▁to ▁the ▁next . ▁In ▁post ▁processing ▁this ▁can ▁be ▁track ed ▁consec ut ively ▁frame ▁to ▁frame ▁and ▁ultimately ▁resolved ▁into ▁angle - in dependent ▁two - dimensional ▁( 2 D ) ▁and ▁three - dimensional ▁stra in - based ▁sequences ▁( 3 D ). ▁These ▁sequences ▁provide ▁both ▁quant itative ▁and ▁qual itative ▁information ▁regarding ▁t issue ▁de formation ▁and ▁motion . ▁ ▁Basic ▁principles ▁ ▁As ▁the ▁spe ck le ▁pattern ▁is ▁random , ▁any ▁region ▁of ▁the ▁my oc ard ium ▁has ▁a ▁unique ▁spe ck le ▁pattern : ▁Within ▁the ▁picture , ▁a ▁defined ▁area ▁" kernel " ▁can ▁be ▁defined , ▁and ▁as ▁this ▁spe ck le ▁pattern ▁is ▁relatively ▁stable , ▁the ▁kernel ▁can ▁be ▁recogn ised ▁in ▁the ▁next ▁frame , ▁within ▁a ▁larger ▁search ▁area , ▁by ▁a ▁" best ▁match " ▁search