The present inventive concepts comprises linearly  polariz­ ing light, splitting the linearly polarized light into a first light and a second light, modulating the first light and the second light to have a phase difference to produce an output wave light, converting the output wave light to have a linear shape in a first direction to radiate the converted output wave light to a measured object, receiving a measurement light coming out of the measured object and linearly polarizing the first light and  the second  light of the measurement light to generate an interference light, and obtaining from the inter­ ference light an image of the measured object. The measured object can be scanned in a second direction intersecting the first direction or may be scanned rotationally about an axis in  a third  direction  perpendicular to  the first and  second directions.