A lensmeter ama lensometer, oo sidoo kale loo yaqaano focimeter ama vertometer, waa qalab indhaha ah. Inta badan waxa isticmaala dhakhaatiirta indhaha iyo kuwa indhaha si ay u xaqiijiyaan warqadda saxda ah ee lagu qoray laba muraayadaha indhaha, si ay si sax ah u jiheeyaan oo ay u calaamadiyaan muraayadaha aan go'in, iyo si loo xaqiijiyo kor u qaadista saxda ah ee muraayadaha muraayadaha muraayadaha.