An opthalmologic apparatus has an examination unit including a plurality of examining parts for executing different examinations on an eye to and a driver moving the examination unit in the horizontal direction and in the anteroposterior direction. A sliding cam slideably received in the housing defines concave portions and an axial hole. In the second interpolation pass, missing on-block pixels, which are the pixels on a block edge formed by two adjacent original pixels, are given values by gradient diffusion based upon interpolation of the values of those adjacent original pixels and the previously interpolated values of their adjacent in-block pixels.